In 1996, Congress expanded the federal Gun Control Act (GCA) to prohibit defendants convicted of a qualifying domestic violence misdemeanor from possessing or purchasing a firearm. Using the FBI's Supplementary Homicide Reports along with homicide data collected from selected state law enforcement agencies, I investigate if this expansion was successful in reducing homicides among the target groups. I use variation from a legal loophole and a series of circuit court decisions to generate difference‐in‐differences estimates. I find evidence that the GCA expansion led to 17 percent fewer gun‐related homicides among female intimate partner victims and 31 percent fewer gun homicides among male domestic child victims. The law also has protective benefits for those that were not targeted by the legislation. “Other” family members (parents and siblings) also experience a 24 percent reduction in gun homicides. I find no evidence that reductions in gun homicides were offset by an increase in nongun homicides. While most falsification and robustness tests support the above conclusions, some tests suggest caution when interpreting the results and a need for further research.

INTRODUCTION Domestic violence is a serious and pervasive social problem. Although victims may be male or female, women are disproportionately affected. One in four women will experience domestic violence at some point in her lifetime (Tjaden & Thoennes, 2000), and women are much more likely to experience extreme abuse, including homicide,1 than are male victims of abuse. Between 1980 and 2008, there were approximately 1,620 domestic homicides annually, and firearms were used in 55 percent of these homicides.2 In addition to firearms’ prominence in intimate partner homicides, studies have also identified a link between a batterer's access to firearms and an increase in the severity of physical abuse they inflict on their partners (Bailey et al., 1997; Campbell et al., 2003). Homes that have a history of domestic violence and where guns are also present are 20 times more likely to experience an intimate partner homicide than homes with a history of domestic violence but where no gun is present (Kellermann et al., 1993). In the mid‐1990s, the federal government recognized the dangerous role of firearms in intimate and domestic relationships. The Gun Control Act (GCA) of 1968 prohibits certain groups (e.g., convicted felons, minors, those addicted to controlled substances, among others)3 from possessing or purchasing firearms or ammunition,4 and in 1996 the GCA was expanded to ban those with a qualifying misdemeanor conviction of domestic violence from possessing a firearm. The focus of this paper is to determine if this expansion achieved its purpose of reducing homicides among intimate partners and domestic children.5 For though advocates hailed this expansion as lifesaving legislation, to my knowledge, no paper has ever researched the effect of this expansion.6 The policy effects of the GCA as well as its expansions have been of interest to researchers and policymakers, but the GCA, with this expansion being the sole exception, has always been uniformly implemented throughout the country. With no timing variation or comparison group available to evaluate the federal gun ban, researchers have had to surmise what its effect might be based on studies of local‐ or state‐level policies. Unlike the GCA or its other expansions, awkward syntax in the 1996 GCA expansion led to the uneven implementation of the policy. The poorly written expansion resulted in unintended, state‐by‐state implementation of the 1996 expansion. The inadvertent departure from uniform implementation provides exogenous treatment variation, which allows me to use a difference‐in‐differences (DD) estimator to evaluate the impact the ban had on family homicides. Simply stated, I will compare the change in the homicide rate among the federally defined domestic violence groups (i.e., domestic relationships defined by the expansion) in states where the expansion applied to the change for the same groups in states without the expansion.7 In addition to knowing if domestic homicides were reduced, it is also of interest to see if the weapon used in homicides was simply substituted away from firearms to a “nongun” weapon such as a knife, arson, blunt force trauma, etc. Such a substitution would clearly frustrate the purpose of the policy. As is common in the literature, I use the FBI Supplementary Homicide Reports (SHRs) to obtain the annual number of homicides in a given state.8 While this data source is widely used, it has missing data problems. States voluntarily provide their homicide counts to the FBI, which has led to an undercount of the number of homicides (Duggan, 2001, offers that 5 to 8 percent of homicides are not reported to the FBI each year). In order to improve the data, I contacted the states that were either missing data or whose counts of homicides in a given year were a clear outlier. Several states provided their homicide data and I used these “new” data to fill in data for missing years (see Table A1 in Appendix).9 The ability to include these previously missing data improved the analyses by ensuring more states were represented in the study and increased the statistical precision of the estimates.10 I find evidence supporting the conclusion that the GCA expansion led to a substantial and significant gun homicide reduction of 17 percent among female intimate partners and a 31 percent reduction in gun homicides among male domestic child victims. The key findings remain unaltered when I change specifications, alter the panel length, and relax key assumptions used in the baseline analysis. However, I also ran a series of falsification tests, and while findings were largely robust to these tests, some analyses are not definitive—suggesting the need for further research on this topic. This paper will proceed in the following manner: the next section discusses the intention and implementation of the GCA expansion, followed by reviews of the literature with an outline of a conceptual framework for the analysis. Then, I provide an overview of the data and outline the empirical strategy. The following sections provide results, discussion, robustness checks, identification of limitations, and a conclusion.

THE GCA 1996 EXPANSION IN GREATER DETAIL The 1996 expansion of the GCA, or Lautenberg Amendment, was intended to reduce the likelihood that a person convicted of perpetrating family violence had access to a firearm. While felons, including those convicted of committing felonies against family members, were already prohibited from having a firearm by the GCA of 1968, Congress was concerned that: [e]xisting felon‐in‐possession laws… were not keeping firearms out of the hands of domestic abusers, because “many people who engage in serious spousal or child abuse ultimately are not charged with or convicted of felonies”11 (142 Congressional Record 22985, 1996; United States v. Hayes, 2009, p. 10). By expanding the GCA to explicitly include those convicted of a qualifying domestic violence misdemeanor, Congress made it more difficult for convicted batterers to elude the ban by pleading to or being convicted of a misdemeanor rather than a felony.12 The law was retroactive; therefore, defendants convicted both before and after the expansion were subject to the ban United States Public Law 18 U.S.C. s (921)(a)(33)(A) provides: The term “misdemeanor crime of domestic violence” means an offense that (i) is a misdemeanor under Federal, State, or Tribal law; and

(ii) has, as an element, the use or attempted use of physical force, or the threatened use of a deadly weapon, committed by a current or former spouse, parent, or guardian of the victim, by a person with whom the victim shares a child in common, by a person who is cohabitating with or has cohabitated with the victim as a spouse, parent, or guardian, or by a person similarly situated to a spouse, parent, or guardian of the victim. The interpretation of subsection (ii) has been the source of much legal debate, and the debate has centered on the meaning of “element” as used in the above federal statute.13 An “element” is something that the prosecution has a legal duty to prove as fact, and all of a crime's elements must be clearly written in the statute. At the time of the expansion, states’ assault statutes could be categorized into two distinct groups: 1 states with assault statutes that only included or statutorily defined the force element (a “general assault” statute) or (2) states with two types of assault statutes. This latter group had both a general assault statute as well as a statute that included both the force and relationship elements (a “domestic violence assault” statute). When the GCA expansion was passed, the federal government as well as about two‐thirds of states only had a general assault statute. A general assault statute makes assaulting any other person a crime; no specific relationship needs to be established in order to convict someone of assault. The GCA expansion did not prohibit defendants convicted of general assault statutes from having a gun regardless of the relationship between the victim and defendant. The remaining states had, in addition to their general assault statute, a domestic violence assault statute, which is usually identical to a general assault statute except that it specifically requires the prosecution to prove the defendant and victim share a domestic relationship. Except for the relationship element of the offense, the domestic violence statute was in many ways redundant to the general assault statute. The rationale for adopting a domestic violence statute was to underscore that domestic violence was a crime and not merely a “family matter” (Epstein, 1999). While a symbolic distinction at the outset, defendants convicted of domestic violence statutes were subject to the federal gun ban, as these statutes clearly contained both the force and relationship elements in subsection (ii). The preceding description of the GCA expansion can be characterized as a narrow reading of the law. Under this interpretation, two offenders can commit the exact same action (e.g., abuse their spouse), but an offender convicted of a general assault statute may legally have firearms while an offender convicted of a domestic violence assault statute may not legally have firearms. Only offenders convicted in states with a domestic violence assault statute are at risk of having the GCA expansion apply to them. However, this narrow interpretation was repeatedly challenged. From 1996 to 2008, eight out of nine circuit court rulings14 interpreted the criteria outlined in 18 U.S.C. s (921)(a)(33)(A) subsection (ii) as applying to all misdemeanor domestic violence defendants convicted of a general assault statute or a domestic violence assault statute. In these states, while a domestic relationship still needed to exist between the victim and defendant, the Government no longer needed to prove this relationship existed. I will refer to this alternative interpretation of the GCA expansion as a “broad” interpretation because, given this reading, the GCA expansion would apply to all domestic misdemeanants in these states. Importantly, after a circuit court's ruling, this broad interpretation applied to all convicted domestic violence misdemeanants within that circuit court's jurisdiction, which spans several states. The legal controversy about which interpretation should be applied, broad or narrow, ended in 2009 when the Supreme Court decided Hayes. The Court ruled for a broad interpretation of the GCA expansion, and therefore, a defendant found guilty of a general assault or domestic assault statute was subject to the GCA expansion as long as they shared a federally defined relationship with the victim. This sequence of events creates distinct types of domestic violence misdemeanants. The “treated group” is composed of domestic violence offenders in a federally defined domestic violence relationship that live in states where the GCA expansion applied (in states with a domestic violence statute or those with a circuit court that ruled the ban should apply in their jurisdiction). The “comparison group” comprises the same offenders, but they live in states where the GCA expansion did not apply until the Hayes decision. The unintended and irregular implementation of the expansion reduces the likelihood that the results are biased, which would occur if there were some omitted shock causing both the passage of the ban and the change in homicides. Table 1 shows which states exclusively had only a simple assault statute throughout the panel (the comparison states), states that had domestic violence assault statutes in 1996, and the states in jurisdictions where circuit courts ruled the ban applied to all domestic violence offenders and the year of the court's ruling (in the primary analysis, these two latter groups comprise the “treated” states, but I will also present disaggregated results). Additionally, five states (listed in the final column of Table 1) adopted a domestic violence assault statute subsequent to the amendment. Due to endogeneity concerns, the states in these groups are dropped from the primary analysis.15 Table 1. States’ Gun Control Act expansion treatment status Treated group states and the year the GCA expansion applied in their state Comparison group states Simple only statute, no court ruling until Hayes States where GCA in effect in 1996, DV assault statute existed States where GCA became effective due to circuit court decision (year of court decision) Excluded due to policy selection concerns States that adopted DV assault law after 1996, before being required by their circuit courtb Delaware

Kentucky

Maryland

New Jersey

North Carolina

Pennsylvania

Wisconsin Arkansas

California

Hawaii

Idaho

Iowa

Michigan

Minnesota

Montana

New Mexico

Ohio

Oklahoma

Rhode Island

South Carolina

Texas

Vermont

Virginia

West Virginia

Wyoming Alabama (2000) a

Alaska (2003)

Arizona (2003)

Colorado (2006)

Connecticut (2003)

Florida (2000)

Louisiana (2003) a

Maine (1999) a

Massachusetts (1999)

Missouri (1999) a

Nebraska (1999) a

New Hampshire (1999)

New York (2003)

North Dakota (1999) a

Oregon (2003)

South Dakota (1999)

Utah (2006)

Washington (2003) Georgia (1999)

Indiana (1999)

Mississippi (1998)

Nevada (1998)

Tennessee (2000)

LITERATURE REVIEW AND CONCEPTUAL FRAMEWORK How Does the GCA Expansion Actually Work? Before expanding on what empirical effects one might expect to find as a result of the GCA expansion, it is worthwhile to discuss how the GCA expansion works in theory and in practice. Upon being convicted of a qualifying domestic assault crime, the judge is required to explain the consequences to offenders, and this includes the ramifications for firearm possession. Offenders are usually asked to sign a statement that they have been made aware that being found in possession of a firearm could result in federal prosecution. In addition to attesting that they have disposed of old firearms, the defendant is not allowed to possess new firearms. In order to prohibit disqualified individuals from purchasing new firearms, the Brady Act (1993) requires licensed gun dealers in the “primary” market to seek a background check on potential buyers. Cook and Ludwig (2006) point out that the Brady Act did nothing to reform the secondary market, a largely unregulated market that is responsible for supplying about 30 to 40 percent of all new guns (Cook, Molliconi, & Cole, 1995) and is responsible for supplying most of the guns used in criminal activity (Sheley & Wright, 1995; Wright & Rossi, 1994). However, despite background check's concentration on the primary market, since November 20, 1998 through 2009, approximately 188,000 (author's calculation)16 requests for firearm purchase were denied following background checks conducted by the FBI or state agencies because the potential purchaser had a qualifying domestic assault conviction. This represents 11 percent of all denials and is the second most frequent reason a disqualified person is denied purchase of a firearm (only felons are denied more often). While background checks clearly prevent (or at least delay) convicted persons from purchasing firearms, a 2002 report authored by Ekstrand and Burton of the General Accounting Office (GAO) found that detecting a domestic violence conviction is challenging; misdemeanors are often not handled in a “court of record,” making data sharing between agencies difficult. The federal government has allocated $350 million to states since 1996 to improve the quality of background checks and increase data sharing (Ekstrand & Burton, 2002). However, given these enforcement challenges, it is reasonable to ask why one should expect the GCA expansion to have an effect on homicides. Why Expect a Change in Homicides? Becker's (1968) theory of crime assumes that a potential criminal weighs the costs and benefits of committing a crime, and if the expected utility from committing the crime exceeds the expected utility from not committing the crime, a crime is committed. The GCA expansion increases the costs of domestic violence misdemeanor crimes—making them one of the most heavily penalized misdemeanors in the criminal code, but subsequent to a domestic violence conviction, the costs of three other crimes also increase: gun possession, gun‐related assaults (domestic or otherwise), and committing a gun‐related homicide.17 I assume that the law leaves the benefits to engaging in these activities unchanged. Several studies have documented that batterers are sensitive to changes in the “cost” of battering and reduce their battering when the costs increase (Aizer, 2010; Markowitz, 2000; Tauchen, Witte, & Long, 1991). One would expect battering to fall as the costs rise (a potential deterrent effect of the law). More salient to this study, if batterers believe the penalties from the GCA are real costs, then theory predicts a decline in the postconviction stock of firearms in domestic offenders’ homes. Such a change could reduce both domestic gun‐related assaults and homicides. However, the law also makes it more difficult for a convicted domestic offender to obtain a firearm. The regulations from the Brady Act require a background check, and while this system is flawed, it still disrupts the “flow” of firearms (even if temporarily). The nature of domestic violence homicides makes this interruption potentially lifesaving for victims. The GCA Expansion in Context of Domestic Violence The National Coalition Against Domestic Violence (NCADV) describes domestic violence as an intentional “pattern of behavior used to establish power and control over another person” (website, n.d.). Many advocates believe that domestic violence escalates over time with homicide being the most extreme outcome. In a world without the gun ban, domestic violence, and especially violence directed toward intimates, could progress in the following manner. The abuse begins with verbal and emotional abuse but slowly escalates into episodes that might be considered illegal, for example, physical abuse. Even if a person is convicted of a misdemeanor, gun possession is not a federal crime. The violence may continue to escalate into more serious crimes. A victim may try to leave her batterer, exposing herself, children, and family to elevated risk of homicide. If the batterer is charged with a felony, it is possible the charge will be reduced to a misdemeanor, and the conviction will still have no implications for the offender's gun ownership. Only after a felony conviction occurs will it be illegal for the offender to have a gun, and the victim's risk of gun‐related homicide will now decline. The time it takes a relationship to progress from an early stage of violence (intimidation) to a more serious stage (felony assault) is unclear, but it is likely a number of years. In contrast, had the expansion been in effect, the batterer would not be able to legally possess a gun after the first misdemeanor conviction, perhaps several years earlier. After a domestic violence conviction, the mere act of owning a gun carries a hefty penalty. If this penalty is enough to effectively dissuade batterers from having a gun, then the GCA expansion is likely to reduce victims’ risk of homicide in at least four ways: Preconviction The GCA expansion increases the cost of misdemeanor assault by permanently criminalizing gun possession and ownership. If offenders or potential offenders are aware of the consequences of domestic violence convictions and value their gun rights, then they may be dissuaded from committing domestic misdemeanor assaults, keeping relationship violence at nonlethal and even noncriminal levels. Postconviction 2. Guns are removed from violent homes at a much earlier stage (i.e., the stock is reduced), which reduces a victim's risk of homicide much earlier. Studies have linked a batterer's access to firearms with an increase in the severity of physical abuse they inflict on their partners (Bailey et al., 1997; Campbell et al., 2003). Additionally, the absence of a gun reduces the likelihood that a physical altercation will unintentionally turn lethal.

3. Victims are at an elevated risk of homicide when they leave an abusive relationship (Campbell et al., 2003). When victims experience this sudden spike in elevated risk of homicide, laws that disrupt an offender's immediate access to new firearms (the flow of firearms) may prove particularly protective.

4. Finally, the GCA expansion increases a convicted batterers’ potential penalty after committing an assault or murder with a gun, which makes committing these crimes more costly. The batterer is subject to any sentencing that may result from the underlying crime as well as additional penalties for gun possession. The GCA expansion also included children as a protected group, making them a clear group of policy and evaluation interest. Children living in homes with domestic abuse are likely to be abused or neglected (Hangen, 1994; Straus, Gelles, & Smith, 1990) and are likely affected by the violence in their homes (Carrell & Hoekstra, 2012). Unlike adult women, children are more likely to be killed by a nongun weapon (see Figures A1 and A2 in Appendix),18 and so the GCA expansion may not afford them as much protection against homicide. Children may be involved in domestic violence as the primary victim, but they may also become involved because they try to protect their mothers from abuse (Hilberman & Munson, 1977–1978). Unlike female children, male children are especially likely to assume a protector role and, in doing so, they risk injury (NCADV, n.d.; Roy, 1988). Little research has been conducted to address the efficacy of current gun control laws on reducing domestic homicides. Vigdor and Mercy (2003, 2006) evaluated state laws’ effect on intimate partners. They find that state‐level domestic violence misdemeanor gun control laws have no effect on intimate partner homicides. While this is disheartening, one might expect federal laws to be more efficacious than state laws. The federal government has more resources than states, the federal government can help to coordinate federal databases thereby improving the flow of information (Ekstrand & Burton, 2002), and federal penalties are much harsher than state penalties. Therefore, the federal policy may have a different effect than state‐level policies.

DATA The data used in this study come from a variety of sources. Homicide counts come primarily from the FBI SHRs, which are compiled and made publically available by the FBI (I use reports from 1980 to 2008 for the primary analysis). While this data set is widely used in research and thought to be the most complete compilation of national homicides, it is not perfect. Law enforcement agencies voluntarily send their homicide counts to the FBI; the voluntary nature means that data for some states for a few years are missing while other states have opted not to participate. When the state's data were missing, I requested homicide data from the state's central law enforcement office. I was successful in obtaining data from several states and used those data to create a more complete homicide data set. After this process, I constructed a data set with 1,381 state‐by‐year cells that contained total homicide counts (see Table A1 in Appendix).19 An additional five states were dropped due to concerns about endogenous policy adoption (Table 1), yielding a final data set with 1,236 state‐by‐year cells. The SHRs contain incident level data, where each observation is a murder event. Demographic information about the age, sex, and race of the victim and offender, the state where the homicide occurred, the year the homicide occurred, the weapon used in the homicide, and the relationship between the primary victim and offender is included. While most observations (97 percent) only involve a single victim and single offender, some observations involve more than one victim or offender (e.g., if a person killed their spouse and child this would be classified as a multiple victim, single offender observation). Most researchers only keep single victim, single offender observations, because the data only reveal the relationship between the offender and one of the victims (what I refer to as the primary victim). However, I have chosen to use information on the sex and age of the additional victims (secondary victims) to make assumptions about their relationship to the offender.20, 21 These assumptions allow me to include these homicides in the analysis, which is important for several reasons: this creates a more complete count of the number of people murdered and it is possible that changes in gun laws could disproportionately change the number of multiple‐victim events. All coding rules for how secondary victims were classified can be found in the Appendix.22 Table 2 provides the number of murder victims by their relationship status and murder weapon for the analytic sample. Table 2. Homicide counts by relationship type and weapon for analytic data set using FBI supplementary homicide data (1980 to 2008) Nongun homicides Gun homicides Total homicides Proportion gun homicides Intimates Husband 2,044 4,781 6,825 0.70 Wife 5,602 11,466 17,068 0.67 Ex‐husband 74 372 446 0.83 Ex‐wife 338 980 1,318 0.74 Common‐law husband 793 747 1,540 0.49 Common‐law wife 805 1,109 1,914 0.58 Domestic children Daughter 4,090 889 4,979 0.18 Stepdaughter 327 127 454 0.28 Son 4,912 1,761 6,673 0.26 Stepson 409 372 781 0.48 Live‐in child 24 5 29 0.17 Total 19,418 22,609 42,027 0.54 I start by aggregating the homicide counts into state‐by‐year relationship‐specific counts. There are two relationships of interest: 1 intimate partners (current and former spouses and common‐law spouses), and (2) domestic children (children and stepchildren). Dating couples present a particular challenge for this analysis. Not all dating relationships are considered domestic relationships by the federal statutes—only couples who have lived together or have had a child together meet the federal definition. Unfortunately, the FBI reports do not reveal dating history, cohabitation status, or other information that would allow me to determine if a couple met the federal definition. While these relationships comprise a nontrivial portion (about 25 percent) of intimate relationships in the data set, I do not present results for this group because it is unclear who is in the dating category and how this mix changes over time. Once the homicides are broken into relationship‐by‐state‐by‐year counts, I further separate them into gun and nongun counts. Only one weapon is identified on the FBI reports, and so the gun plus nongun counts sum to the homicide counts. I repeat this process for male and female victims. Intimate partner homicides have been declining in the United States for several decades. Of interest to this paper is determining if the GCA expansion accelerated this decline among the treated groups. I provide a series of graphs (see Figures A1 and A2 in Appendix)23 plotting the trend in the overall homicide rate, the gun homicide rate, and the nongun homicide rate for male and female victims. Figure A1 shows trends in the states where the GCA expansion applies and Figure A2 shows trends in states where the GCA expansion never applies (all rates are weighted by state population). Since policy implementation dates vary, I graph the “year since change” rates making “Year ‐1” the year before the policy change, “Year 0” the year of change, etc., and in the comparison states, “Year since change” is benchmarked to 1996. In these figures, one can see that intimates are more vulnerable to gun homicides and that intimate homicide trends are very different from domestic child homicide trends. It is also evident that men and women often have different trends, with men experiencing steeper and more sustained declines in homicides. Gun homicides comprise the majority of female intimate homicides, but the threat of gun relative to nongun homicide has particularly diminished for men. Also, adult men and all children are at a much higher risk of a nongun homicide relative to gun homicide. This variation motivates running aggregate and group‐specific regressions. Given the differences in how males and females are affected by domestic violence, I will also disaggregate the analyses by victims’ sex. I use an indicator variable to represent when domestic batterers were subject to the GCA expansion in a given state (Table 1).24 I collected these dates through a series of sources (WestLaw, state legal or legislative law librarians, the American Bar Associations, Commission on Domestic Violence, and federal circuit court websites). The first step was to identify states with a domestic assault statute. If states had these statutes in place when the GCA expansion was passed, then the GCA expansion dummy variable turned on in 1996. The next step was to identify when relevant circuit court decisions were made. If a state had a simple assault statute and its governing circuit court ruled that the GCA expansion applied to all domestic batterers regardless of the title of the statute or whether or not the statute delineated the relationships in its text, the dummy variable turned on in the year the decision was made.25 If a state passed a domestic violence statute after 1996 and they were not already bound to adhere to the GCA expansion due to a circuit court ruling, the state was dropped from the primary analysis. It may be that these states were endogenously adopting these laws in response to the GCA expansion (GAO 2002).26 It is possible that a state could have had both a domestic violence statute and was then later also affected by a Circuit Court ruling. In the event this “double‐treatment” matters, I created an additional dummy variable that turns on in the state‐year observation where both types of GCA expansion treatment apply. Ideally, I would also like to control for the state's desire to respond aggressively toward extreme domestic or gun violence. I use an indicator variable that turns on in the state‐year observation where the federal prosecutor charged a defendant only convicted of a general assault statute with violating the GCA. The variable remains on throughout the time series, except for West Virginia, where the fourth circuit ruled the GCA expansion did not apply to persons with only a general assault conviction. I also control for the state's crime and prosecutorial environment more broadly. As a proxy for violent crime, I control for the robbery rate using data from the FBI's Uniform Crime Reporting Database.27 In the main analysis, I control for states’ death penalty laws (Amnesty International, n.d.)—though this is not an ideal measure because it is time invariant for many states. I would prefer to use state‐year prison admissions rates, but these data are only available for a subset of the sample, and so I will use this variable in a robustness test, which I will describe later in the paper. The presence of other domestic violence laws, for example, having a domestic violence assault statute, having a state‐level gun ban on those convicted of a domestic violence misdemeanor, having Orders of Protection (this is not controlled for as there is little variation across states), and prohibiting those under Orders of Protection or ex‐parte Orders of Protection28 from having guns, may have their own independent effect on homicides. If a state has one of these complementary laws, an indicator variable is used (equal to one when the law is in effect and 0 otherwise). In order to determine which states have these laws and when they became effective, I used an analogous procedure to the one used to determine information about states’ assault statutes, though to control for state gun bans I follow Vigdor and Mercy (2006). I also control for unilateral divorce laws (coding follows Stevenson & Wolfers, 2006). Domestic violence laws and unilateral divorce laws serve as a proxy for states that devote additional resources to or are particularly sensitive to “women's” issues. Table A2 (Appendix)29 provides summary statistics for the independent variables used in the analysis. Adjusted regressions contain controls for other annual state‐level socioeconomic characteristics. I use the March CPS (King et al., 2004—distributed through IPUMS) to construct race variables (proportion white, African American, and other), marital status (proportion married, single, divorced, and widowed), the average household income, and the female to male employment ratio. I also obtained the AFDC/TANF maximum benefit level for a family of three and the state poverty rate from the University of Kentucky's Poverty Research Center. The population at risk30 is used to transform homicide, gun, and nongun counts into rates. I calculated the population at risk by using the annual state population estimates from the U.S. Census Bureau and state‐year relationship estimates from the March CPS (see Appendix).31

EMPIRICAL STRATEGY I use a DD estimator to obtain the average treatment effect of the GCA expansion. The DD coefficient represents an estimate of the change in the homicide rate for the domestic group(s) in states where the gun ban applied less the change in the homicide rate for the domestic group(s) in states where the gun ban never applied (the counterfactual). An identifying assumption of the model is that the difference in homicide rates would have remained the same in the absence of the GCA expansion. I will relax this assumption by conditioning on state‐specific linear trends and covariates, but this comparison seems reasonable for at least two reasons. Figure 1 shows overall homicide trends across the three types of states (states where the expansion initially applied, states whose circuit court ruled the expansion should apply, and the comparison states); the trend lines are quite similar.32 As the policy was unintentionally applied to some states and not others, the threat from selection into treatment is lessened. Figure 1 Open in figure viewerPowerPoint Homicide Rate Trends for Domestic Groups. Notes: All rates are weighted by the state's annual population. Vertical line marks 1996, the year the Gun Control Act expansion was passed. However, it is true that certain pretreatment characteristics (whether or not the state had a domestic violence statute, for example) determined where the ban would apply. Vigdor and Mercy (2003, 2006) establish that states with domestic violence statutes are different on a number of socioeconomic conditions, and these covariates should be controlled for in the analysis to eliminate bias in the estimated treatment effect. In the absence of randomization, I cannot be sure that the estimation strategy is unbiased, but models that include trends and models that include trends as well as time varying controls are very similar, which provides some evidence that the estimated treatment effect is robust. I use weighted least squares (WLS)33 regression and equation 1 to assess the impact of the GCA expansion. In equation 1, the estimated coefficient for β1 is the DD estimate. If the coefficient is negative (positive), this implies the GCA expansion decreased (increased) homicides relative to what would have happened without the policy. GCA is the weighted indicator variable (see footnote 23) that turns on in the states subject to the ban in the year the ban became effective, X is a vector of state‐level, time varying controls, λ is a vector of state fixed effects, Γ is a vector of year effects, Θs × Year is a vector of state‐specific trends, and εst is a random error term. The dependent variable is the group homicide, gun, or nongun rate. (1) I run separate group‐specific models with the gun and nongun rates as the dependent variables. All regressions use Huber–White standard errors clustered at the state level and are weighted by the total population in a given state in a given year. While the above equation is my preferred specification, I also present results from a model without trends or covariates (Model 1) and a model with trends but no covariates (Model 2). Model 3 refers to regressions that include all covariates and trends, which are very important for the specification of the model.34 Domestic violence, and in particular, lethal violence has been trending downward in a linear fashion since the 1970s (see Figure 1). While the time effect will control for national events, a state‐specific trend is needed to account for gradual social and demographic changes in each state. Social changes such as women's economic advancement, changes in reproductive policy, and increased awareness about family violence all occurred at different rates and to different degrees in the states. Such covariates would be hard to measure and explicitly control for in the model. The state‐specific linear trends35 help to capture these very important omitted variables. Once these trends are controlled for, the DD coefficient is robust to model choice, particularly among female intimate partners and male domestic children victims, and this helps to bolster the claim that the GCA expansion is not correlated with state‐level unobserved heterogeneity.

RESULTS AND DISCUSSION Main Results Results showing the impact the expansion had on homicides among intimate partner relationships can be found in the top panel of Table 3. While results for Models 1, 2, and 3 are shown, I focus my discussion on results from Model 3. In addition to providing the coefficients, I discuss the corresponding percent change, which is calculated by dividing the DD coefficient by the average of the dependent variable. The first set of results considers the effect of the ban on all intimates, females and males combined. Results from Model 3 imply that the expansion reduced the intimate partner gun homicide rate36 by a statistically significant 0.0667 (or 11.44 percent)37 and no significant change in nongun homicide rates is observed. Table 3. GCA expansion's effect on intimate partner and domestic children's homicide rates (1980 to 2008) All victims Model 1 gun rate Model 2 gun rate Model 3 gun rate Model 1 nongun rate Model 2 nongun rate Model 3 nongun rate All intimate partners DD coefficient −0.184* −0.0645* −0.0667** −0.0219 0.00367 −0.0005 (0.0939) (0.0325) (0.0309) (0.0172) (0.0151) (0.0142) Average homicide rate 0.583 0.2928 Percent change −31.56% −11.06% −11.44% −7.48% 1.25% −0.17% R2 0.748 0.883 0.888 0.579 0.635 0.641 Female intimate partners DD coefficient −0.182** −0.136*** −0.136*** −0.0262 0.0121 −0.0053 (0.0865) (0.0433) (0.0443) (0.0271) (0.0268) (0.0286) Average homicide rate 0.7869 0.3955 Percent change −23.13% −17.28% −17.28% −6.62% 3.06% −1.34% R2 0.727 0.800 0.804 0.379 0.426 0.439 Male intimate partners DD coefficient −0.187 0.0107 0.0053 −0.0177 −0.0058 0.0037 (0.114) (0.0413) (0.0312) (0.0193) (0.0144) (0.0180) Average homicide rate 0.3644 0.1824 Percent change −51.32% 2.94% 1.45% −9.70% −3.18% 2.03% R2 0.644 0.860 0.869 0.542 0.614 0.622 All domestic children DD coefficient −0.0429** −0.0276 −0.0348** −0.0146 0.0011 −0.0292 (0.0173) (0.0165) (0.0165) (0.0327) (0.0250) (0.0332) Average homicide rate 0.1418 0.4419 Percent change −30.25% −19.46% −24.54% −3.30% 0.25% −7.51% R2 0.422 0.469 0.479 0.326 0.392 0.413 Female domestic children DD coefficient −0.0326*** −0.0132 −0.0113 0.00253 0.0218 −0.0062 (0.0110) (0.0146) (0.0149) (0.0413) (0.0392) (0.0476) Average homicide rate 0.1027 0.4462 Percent change −31.74% −12.85% −11.00% 0.57% 4.89% −1.39% R2 0.156 0.190 0.207 0.184 0.234 0.254 Male domestic children DD coefficient −0.0550* −0.0426* −0.0586** −0.0305 −0.0120 −0.0476 (0.0300) (0.0251) (0.0244) (0.0328) (0.0261) (0.0340) Average homicide rate 0.1896 0.4765 Percent change −29.01% −22.47% −30.91% −6.40% −2.52% −9.99% R2 0.399 0.450 0.459 0.261 0.321 0.339 State and time effect? Y Y Y Y Y Y Linear time trend? N Y Y N Y Y State‐level covariates N N Y N N Y Sample size 1,236 1,236 1,236 1,236 1,236 1,236 Moving down Table 3, one finds the effect of the expansion on gun and nongun homicide rates among female intimate victims (wives, former wives, and common‐law wives). The DD estimator changes slightly depending on the model (estimates from Model 1 are larger than those from Models 2 and 3), but Model 3 indicates the expansion led to a significant decline of 0.136 in the female intimate partner gun homicide rate (a 17 percent reduction). A percent reduction of this magnitude would translate into approximately 80 fewer female intimate gun‐related homicides annually. There is no evidence that female intimates experience increased nongun‐related homicides following the expansion. Table 3 then contains the results for gun and nongun homicide rates among male intimate victims (husbands, former husbands, and common‐law husbands). These results reveal that the gun ban had very little effect on these crimes; the coefficients from Models 2 and 3 are small in their relative magnitude and are not statistically significant. This analysis provides evidence that, among intimate partners, the GCA expansion's effect is isolated to gun homicides perpetrated against female intimate partners. The lower half of Table 3 details the results for domestic children (sons, stepsons, daughters, stepdaughters, and “live‐in‐children”). Results from Model 3 imply that the GCA expansion reduced the gun homicide rate among domestic children by a significant 0.0348, which corresponds to a 25 percent decline, and as with intimate partners, there does not seem to be a corresponding increase in nongun homicides. When the domestic children are disaggregated into males and females, the regressions reveal that this decline is concentrated among male victims. Model 3 shows that gun homicide rates for male domestic children declines by 0.0586 (or 31 percent) following the expansion. While this percent change is larger than the one experienced by female intimates, the average gun homicide rate for domestic children is much smaller than it is for female intimates. Therefore, this reduction would result in approximately 23 fewer young men murdered annually by guns. Furthermore, unlike intimate partner victims, nongun weapons are used in the majority of homicides committed against children. Therefore, it is important to realize that changes in gun homicides will not have as large an impact on overall homicides for (male) domestic children. The GCA expansion's potential effect on male domestic children but not on female domestic children is consistent with the previously reviewed literature. Female intimates are more often the victim of extreme domestic abuse, and are, therefore, at an elevated risk of domestic homicide relative to males. Male domestic children may experience a reduction in gun‐related homicide while female children do not, perhaps because male children are more likely to protect their mothers from their abusers (this may be especially true of stepsons, who comprise nearly half of all child victims). By protecting their mothers, male domestic children are at an elevated risk of harm. However, as mothers are exposed to less gun violence (or at least gun homicide) then male children are exposed to fewer incidents of domestic abuse (or fewer episodes with guns). As a consequence, male domestic children's risk of gun‐related homicide declines more so than female domestic children's risk. It is possible that the GCA expansion has a different effect depending on how the GCA expansion was adopted by the state, either by having a qualifying domestic violence assault statute or through a circuit court ruling. Table 4 presents results from a model that decomposes the treatment into two parts yielding a DD coefficient for domestic violence assault statute states and a DD coefficient for circuit court states. The upper panel of the table presents the effect of the decomposed treatments on total, gun, and nongun homicide rates for intimate partners, and the lower panel presents the same results for domestic children. Among female intimates, the DD coefficients for the two treatment groups are similar in magnitude and not statistically different. A similar pattern holds for male domestic children; the coefficients are similar in magnitude and they are not statistically different. For male intimates, while the DD coefficients appear to be quite different and opposite signed, they are only statistically different at the 10 percent level. Despite this strange finding, among the two groups where a clear treatment effect appears, the manner in which the GCA expansion was introduced into the state's legal apparatus appears to have no meaningful impact on the treatment effect. Table 4. GCA expansion's effect with decomposed treatment groups (1980 to 2008) Both sexes Female victims Male victims Homicide rate Gun rate Nongun rate Homicide rate Gun rate Nongun rate Homicide rate Gun rate Nongun rate Intimates DV assault −0.0051 −0.0133 0.0081 −0.152** −0.157** 0.0048 0.1470** 0.136** 0.0107 states (0.0454) (0.0330) (0.0293) (0.0715) (0.0610) (0.0363) (0.0590) (0.0604) (0.0385) Circuit court −0.111** −0.104* −0.0067 −0.133** −0.120** −0.0127 −0.0885 −0.0872 −0.0013 states (0.0487) (0.0523) (0.0283) (0.0540) (0.0496) (0.0471) (0.0678) (0.0693) (0.0234) t‐Test of difference 1.5067 1.3491 0.3000 0.2236 0.5568 0.2646 2.2405** 1.8708* 0.2449 Domestic DV assault −0.113** −0.0390 −0.0738 −0.0678 −0.0416 −0.0262 −0.1560*** −0.0399 −0.116* children states (0.0530) (0.0272) (0.0631) (0.0848) (0.0271) (0.0863) (0.0507) (0.0391) (0.0665) Circuit court −0.0305 −0.0319** 0.0014 0.0169 0.0102 0.0067 −0.0721* −0.0719*** −0.0002 states (0.0360) (0.0151) (0.0317) (0.0543) (0.0159) (0.0528) (0.0403) (0.0250) (0.0280) t‐Test of difference 1.2000 0.2646 1.0392 0.8307 1.7205* 0.3162 1.0863 0.7550 1.5748 Robustness and Specification Checks An alternative research design would have used a within‐state control group to determine if the GCA expansion reduced homicides among intimates and domestic children. One potential comparison group would have been other domestic groups not targeted by the GCA expansion (i.e., parent and sibling victims). However, it is highly probable that this group experiences spillover effects from the law. While female intimates may be the most likely to experience violence and homicide, those around them, including other family members, are also at risk of harm or death (Florida Governor's Task Force on Domestic and Sexual Violence, 1997). There is very little research on the dynamics of nonintimate family violence, but it has been established that the mere presence of a firearm increases the lethality of crime (Cook, 1991; Kellermann et al., 1993; Zimring, 1968). This framework could easily extend to other family members. If a home is gun‐free due to a domestic violence conviction, then when family members engage in violence toward one another, the risk of lethality in these altercations is also reduced. The family is an intertwined unit. It is highly unlikely that the protective effects of the laws are contained to the legislated groups, which would make them an inappropriate comparison group. The top half of Table 5 presents results showing the effects of the GCA expansion on domestic groups (siblings and parents) that were not targeted by the law (also disaggregated by sex). The analysis shows that the GCA expansion significantly reduces the gun homicide rate by 0.0174 for female family members and 0.0572 for male family members. These declines translate into a decline of about 24 percent for both groups, which is approximately 18 annual gun deaths among females and 60 annual gun deaths among males. Men may experience a greater decline in their homicides after the GCA expansion because these family members also engage in protective roles or, alternatively, because arguments between domestic offenders and these victims become less lethal when guns are removed from the home. Table 5. GCA expansion's effect on groups outside of GCA expansion's scope (1980 to 2008) Female victims Male victims Model 1 Model 2 Model 3 Model 1 Model 2 Model 3 Model 1 Model 2 Model 3 Model 1 Model 2 Model 3 Gun Gun Gun Nongun Nongun Nongun Gun Gun Gun Nongun Nongun Nongun Rate Rate Rate Rate Rate Rate Rate Rate Rate Rate Rate Rate Domestic excluded DD coefficient −0.0131* −0.0157* −0.0174** 0.00146 −0.0129 −0.0123 −0.0493 −0.0556** −0.0572** −0.0032 −0.0180 −0.0185 (0.0074) (0.0093) (0.0085) (0.0066) (0.0078) (0.0079) (0.0381) (0.0216) (0.0231) (0.0147) (0.0128) (0.0119) Average homicide rate 0.0716 0.0941 0.2445 0.1455 Percent change −18.30% −21.93% −24.30% 1.55% −13.71% −13.07% −20.16% −22.74% −23.39% −2.20% −12.37% −12.71% R2 0.281 0.333 0.346 0.187 0.224 0.238 0.675 0.767 0.771 0.386 0.444 0.454 Other (nondomestic) DD coefficient −0.102*** −0.0335 −0.0496 −0.0616 0.0043 −0.0119 −1.166** −0.552 −0.735 −0.305* −0.0962 −0.151 (0.0374) (0.0429) (0.0451) (0.0484) (0.0362) (0.0351) (0.471) (0.460) (0.472) (0.175) (0.136) (0.128) Average homicide rate 0.3382 0.4473 3.0374 1.4188 Percent change −30.16% −9.91% −14.67% −13.77% 0.96% −2.66% 38.39% −18.17% −24.20% −21.50% −6.78% −10.64% R2 0.676 0.741 0.754 0.561 0.641 0.658 0.779 0.852 0.870 0.724 0.821 0.834 State and time effect? Y Y Y Y Y Y Y Y Y Y Y Y Linear time trend? N Y Y N Y Y N Y Y N Y Y State‐level covariates N N Y N N Y N N Y N N Y Sample size 1,236 1,236 1,236 1,236 1,236 1,236 1,236 1,236 1,236 1,236 1,236 1,236 Another potential within‐state comparison group is nondomestic “others”—those victims who have no familial relationship with the offender (friends, acquaintances, strangers, etc.). However, this group is inappropriate because the pretreatment homicide (gun and nongun) rate trends follow very different patterns when compared to the domestic groups’ homicide trends. However, while this group does not present an appropriate counterfactual to the domestic groups, there is little reason homicide rates among “other” victims should be substantially affected by the law. Due to a lack of proximity to the family unit, one would not expect the spillover effects described earlier to be experienced by this group.38 The lower half of Table 5 shows results for these groups. In the baseline models (Model 1), the estimates for gun‐related homicides are both statistically significant at the 5 percent level. This may be a potential problem, but statistical significance disappears when controls are added to the model. Despite being insignificant, the estimates remain large in magnitude (models imply a 14 percent reduction for other female gun homicides and a 24 percent reduction for other male gun homicides). This may signal a problem with the overall research design, but the reader is cautioned with interpreting these results as they may suffer from omitted variable bias. States have many policies targeted at stranger‐ or drug‐related crime, which may affect these homicide rates but are not controlled for in the models. In fact there is evidence that bias exists in the models limited to other, nondomestic victims. The DD coefficient varies from Model 1 to Model 2 to Model 3, but the DD coefficient between Models 2 and 3 is much more stable among the domestic groups in the paper. Also, Model 3 among other, nondomestic victims is sensitive to the weighting choice. Solon, Haider, and Wooldridge (2013) indicate this might point to a misspecified model among the other, nondomestic groups. Overall, the results in Table 5 provide assurance—though not concrete evidence—that the results presented in Table 3 are not simply capturing the secular decline in states’ homicide rates39 or some other omitted variable (a state with better or more aggressive prosecutors, other laws to moderate gun control, or a demographic shift). I also conducted a formal test for treatment leads and lags. I follow the Granger causality test suggested by Angrist and Pischke (2009). Instead of using one indicator variable that is equal to 1 in the treated states in the post period, I disaggregate the variable into a sequence of mutually exclusive pretreatment and posttreatment variables. I include a variable if the policy will be available in five or six years (but not fewer), if the policy will be available in three or four years (but not fewer), if the policy will be available in one or two years (but not fewer), a variable to measure the immediate policy effect, a variable if the policy has been available for two or three years (but not fewer), a variable if the policy has been in effect for four or five years (but not fewer), and a variable if the policy has been in effect for six or more years (but not fewer). If a pretreatment variable is significant, this could represent an anticipatory effect. If the decline in homicide rates began before the policy became effective, this could suggest some other, omitted variable is driving the results. Table A3 (Appendix)40 presents the results and no significant anticipatory effects emerge.41, 42 This analysis can also provide evidence about phase‐in effects of the law. While none of the post variables are significant, they do tend to grow in magnitude among female intimates, which implies the policy effect may take time to emerge or it may grow over time. This dynamic is not observed in male domestic children, but given the overall rarity of the outcome, this analysis, which further reduces cell sizes, may be asking too much of the data. Table 6 shows the impact of the GCA expansion on intimate partners and domestic children's gun and nongun homicide rates using a variety of specifications. The first alternative is the Poisson model. The results are roughly the same in terms of magnitude and precision, though the Poisson model hints at a decline in gun homicide rates among female domestic children. Next, I use the log of the gun and nongun homicide rates as the dependent variable. This is not my preferred specification because many state‐year homicide counts are 0, especially among children. These results for female intimates and male children are nearly identical, but in the log models, there is a 20 percent decline in male intimate nongun homicide rates. However, generalization of this latter result is cautioned as nearly half of the sample is missing due to the log transformation. Chalfin and McCrary (2012) suggest a method that allows one to approximate the natural log of a variable without creating missing data when the count is 0. When this technique is employed, results are nearly identical to the main results, and the GCA expansion is found to have no significant effect on male intimate nongun homicide rates. Table 6. Alternative specifications to determine the GCA expansion's effect Gun homicides Nongun homicides Difference‐in‐difference coefficients for: Female intimates Male intimates Female domestic children Male domestic children Female intimates Male intimates Female domestic children Male domestic children Poisson modela −0.201*** 0.104 −0.176* −0.422*** 0.0766 0.0766 0.0766 0.0766 (0.0506) (0.0880) (0.107) (0.150) (0.0790) (0.0790) (0.0790) (0.0790) Sample size 1,236 1,236 1,236 1,236 1,236 1,236 1,236 1,236 Ln(homicide rate) −0.205** 0.0012 0.0536 −0.388** 0.0035 −0.204** 0.0873 −0.0182 (0.0855) (0.0853) (0.140) (0.152) (0.0899) (0.0938) (0.0995) (0.0683) Sample size 1,122 844 493 699 1,004 716 907 940 Ln(homicide count) −0.208** −0.0308 −0.0923 −0.264** −0.0111 −0.0456 0.0258 −0.0515 transformationa,b, a,b (0.0923) (0.100) (0.0830) (0.131) (0.0852) (0.0887) (0.0918) (0.0709) Sample size 1,236 1,236 1,236 1,236 1,236 1,236 1,236 1,236 Models include incarceration −0.129** −0.0120 −0.0303 −0.0665** 0.00358 −0.00501 −0.00970 −0.0132 control (0.0497) (0.0285) (0.0206) (0.0305) (0.0307) (0.0188) (0.0582) (0.0439) Sample size 720 720 720 720 720 720 720 720 Average homicide rate 0.7118 0.2316 0.1040 0.1646 0.3723 0.1434 0.4556 0.4931 Average % Change −18.12% −5.18% −29.14% −40.40% 0.96% −3.49% −2.13% −2.68% Panel length: 1990 to 2008 −0.115** −0.00854 −0.0234 −0.0550* −0.00170 0.00115 −0.00403 −0.0308 (0.0506) (0.0232) (0.0180) (0.0276) (0.0290) (0.0182) (0.0433) (0.0353) Sample size 813 813 813 813 813 813 813 813 Average homicide rate 0.6506 0.2058 0.0963 0.1492 0.3589 0.1294 0.4378 0.4693 Average percent change −17.68% −4.15% −24.31% −36.86% −0.47% 0.89% −0.92% −6.56% Unweighted regressions −0.139** 0.0473 −0.0043 −0.0605** −0.0411 0.027 0.0038 −0.0872** (0.0522) (0.0457) (0.0317) (0.0256) (0.0357) (0.0328) (0.0845) (0.0417) Sample size 1,236 1,236 1,236 1,236 1,236 1,236 1,236 1,236 Average homicide rate 0.7755 0.3601 0.0989 0.1896 0.3598 0.1604 0.4092 0.4324 Average percent change −17.92% 13.14% −4.35% −31.91% −11.42% 16.83% 0.93% −20.17% As previously discussed, one would ideally like to control for the aggressive nature of the prosecutorial environment. If “aggressive” prosecutors are correlated with the implementation of the GCA expansion and a change in homicides, then this would bias the DD coefficients. In order to determine if this threat exists, I constructed adult state‐by‐year prison admissions rates using the National Corrections Reporting Data, which are collected by the Bureau of Justice Statistics. Unfortunately, while more states report prison date over time, data submission is voluntary and is only consistently available for 28 states from 1983 to 2008. I included prison admissions rates as well as prison admissions rates for violent crimes for the state‐year observations where data were available. Inclusion of this variable leaves the results largely unchanged, with the exception being an implied 23 percent reduction in gun homicides among female child domestic victims. I also start the panel in 1990 rather than 1980, and the percent change in homicides does not vary considerably among any of the groups. The magnitude of the DD coefficient among male domestic children's gun homicide rates is similar to before, but it is now only significant at the 10 percent level. Given the reduction in the sample size, this is not surprising. I weighted the regressions to correct for population‐size‐related heteroskedasticity in the state‐year error terms. I follow suggestions made by Solon, Haider, and Wooldridge (2013) to determine if weighting is advisable, but the statistical evidence I obtained regarding weighting was mixed. Therefore, I also present unweighted estimates. The estimated reduction in gun‐related female intimates and male domestic children is very similar to those presented in Table 3, Model 3. However, a statistically significant decline in nongun male domestic children homicides also emerges. Unweighted regressions that do not control for state trends or covariates (Model 1) find no effect of the GCA expansion on any of the groups analyzed in this paper. Finally, I evaluate the importance of two research decisions I made. Instead of imputing the victim and offender's relationship, I limit the sample to primary victims. I also include the states that may have endogenously adopted a Domestic Violence Assault Statute in order to make the GCA expansion binding in their state. Results are robust to both of these choices and are available upon request.

LIMITATIONS It is possible my description of how the gun ban “rolled out” in certain states is wrong. If the states I have identified as the comparison group interpreted the GCA expansion as Congress intended, then they would have enforced the expansion. In the context of an experiment, the “comparison group” would be receiving the treatment and is “contaminated.” In the absence of a circuit court appeal, there is no definitive way to know how federal courts in those states handled or struggled with these issues, but the absence of these appeals is actually informative and supportive of my explanation of events. If a federal prosecutor attempted to charge a defendant in the comparison states with violating the GCA expansion, a defense attorney would have likely made a motion to have the charges dropped because the elements of the crime were not met (i.e., the defendant was never convicted of a qualifying domestic charge and therefore could not, by legal definition, be guilty of violating the GCA). This is the legal argument for all of the appeals in the circuit courts used in this analysis, but such appeals never occurred in the comparison states. Even still, it is possible to think through the implications of this limitation. If the “comparison states” were enforcing the ban, and if the GCA expansion has a protective effect, then gun homicide rates in those states would also be reduced. The estimated difference between the treated and comparison states would be attenuated. Thus, if this limitation exists, one should view the results presented here as a conservative estimate of the treatment effect. Ideally, one would like to explore the mechanisms by which the gun ban generates a reduction in gun homicides. Earlier I outlined at least four ways the gun ban might reduce gun, and even nongun, homicides. One might be more convinced if I could demonstrate that after the policy change there was a change in an intermediate outcome, which then led to a change in the gun homicide rate. In particular, one might want evidence that state‐by‐year gun ownership rates are declining in the treated states, especially among convicted domestic violence offenders. Unfortunately, this type of data does not (to the best of my knowledge) exist. Also of interest would be to understand the GCA expansion's impact on intermediate injury outcomes. With appropriate data one could examine if attempted murders or other serious assaults responded to the GCA expansion. The FBI homicide data only contain completed homicides, and while this is informative and of interest, many less severe abusive events do not make it into the data. Furthermore, the GCA expansion makes domestic violence crimes more costly, and if these crimes happen less frequently, this might mean the escalation of domestic violence is slowing. Examples of data that might answer these questions would include hospital injury data or more frequent national surveys regarding domestic violence. To my knowledge, such data are not readily available to the research community. Finally, it is important to remember that my estimation strategy capitalizes on variation resulting from different states adopting the GCA expansion at different times. This is a quasi‐experimental design, and as such, I cannot perfectly rule out potentially confounding explanations. While the findings presented in this paper support well‐tailored gun restrictions, additional research is needed to support the findings in this paper.

CONCLUSION Despite the policy importance and public interest surrounding the federal GCA, this legislation has never—to my knowledge—been evaluated. This study, however, takes advantage of policy implementation variation to provide the first evaluation of any part of the GCA. I find evidence that the 1996 GCA expansion was successful in reducing gun‐related homicides among female intimates by approximately 17 percent and male domestic children by an estimated 31 percent. In addition, other family members (siblings and parents), though not directly included in the law's language, also experience a reduction in gun‐related homicides following the expansion. These declines in gun‐related homicides are particularly noteworthy as there was no corresponding increase in nongun homicides among these groups. The results presented capture the additional reduction in homicides following the expansion while controlling for the effect of other state gun laws. It is important for the reader to bear in mind the limitations of this work. While the FBI data are a well‐established source of information in the research community, missing and inconsistent data are problematic. Although I collected and integrated previously missing FBI homicide reports to partially address this concern, some observations were unavailable. Specifically, Kansas, Illinois, and Washington, DC are omitted from the analysis entirely while other states have some missing observations. Moreover, while the results are robust to a number of alternative specifications, some models hint that the assumptions of the DD model are not met. For example, even my preferred model (Model 3) indicates sizeable, although statistically insignificant, reductions in gun homicides among other nondomestic groups. Finally, while homicides are a violent act of policy interest, this research does not speak to the effect of the law on intermediate injuries, for example, gunshot wounds or assaults. Studies of these intervening outcomes would improve our understanding about the policy's mechanisms. In closing, this study contributes to a growing literature regarding the impact of criminal justice system interventions on family violence, and in doing so sparks the need for future work on at least two important policy dimensions. The first relates to understanding why federal gun restrictions were successful in reducing domestic homicides when state‐level gun restrictions were not successful. The federal law is distinct from state laws in several ways: it is retroactive and permanent, there are no public service exemptions, the penalties for violation are usually much larger than those allowed by state laws, and sizable federal resources—especially those related to enhancing the background check system—likely bolster the effectiveness of the law. Future work should seek to understand which of these distinctions matters as this might be critical to the success of future gun or family violence legislation. A second important area for future research is investigating why domestic batterers are sensitive to federal gun restrictions. Did the GCA expansion reduce the stock or flow of guns or both? Are batterers more sensitive to criminal penalties relative to individuals that commit other types of crimes? How does violence between an intimate couple affect the safety of other members of a family? Understanding the answers to these questions would assist policymakers in crafting future legislation geared toward reducing family violence, which may in turn save lives.

ACKNOWLEDGMENTS I acknowledge and am thankful for dissertation research funding provided by the Doris Duke Charitable Foundation. I am grateful to Len Lopoo, Bob Bifulco, Anna Aizer, Doug Wolf, Len Burman, Jens Ludwig, Kristin Seefeldt, Dave Muraskin, Coady Wing, Jessica Su, Lincoln Groves, Ken Couch, anonymous reviewers, and participants at the 2011 Annual Meetings of APPAM for their helpful insights and valuable comments. I thank the states that provided their homicide data, data analysts at the FBI for answering many questions, and the many law librarians and legislative researchers who provided me with historical, legal documents, and effective dates. All remaining errors are my own.

1 The term “homicide” has a broad legal meaning. In this paper, it is used to mean the killing of another person.

The term “homicide” has a broad legal meaning. In this paper, it is used to mean the killing of another person. 2 Both statistics were generated by the author using FBI data for all states for which data are available and using the federal definition of domestic groups. If dating relationships are included, the annual number of homicides increases to 2,280.

Both statistics were generated by the author using FBI data for all states for which data are available and using the federal definition of domestic groups. If dating relationships are included, the annual number of homicides increases to 2,280. 3 Prior to 1996, the groups prohibited from owning or possessing a firearm were minors, those under a felony indictment or with a felony conviction, those who have renounced their citizenship, those addicted to controlled substances, those dishonorably discharged from the military, and those with a domestic violence protective order against them (18 U.S.C. s 922(d)(5).1994).

Prior to 1996, the groups prohibited from owning or possessing a firearm were minors, those under a felony indictment or with a felony conviction, those who have renounced their citizenship, those addicted to controlled substances, those dishonorably discharged from the military, and those with a domestic violence protective order against them (18 U.S.C. s 922(d)(5).1994). 4 I will use “possession” to refer to possession and purchase and “firearms” to refer to firearms and ammunition.

I will use “possession” to refer to possession and purchase and “firearms” to refer to firearms and ammunition. 5 There have been other expansions of the GCA, notably the 1994 expansion that prohibited batterers with a current Order of Protection against them from possessing a firearm. I focus on the latter expansion because the effect of the policy can be identified. The initial Act and its former expansions were implemented in all states, to all groups, at one time. The necessary variation needed to be able to identify the model for previous expansions does not exist.

There have been other expansions of the GCA, notably the 1994 expansion that prohibited batterers with a current Order of Protection against them from possessing a firearm. I focus on the latter expansion because the effect of the policy can be identified. The initial Act and its former expansions were implemented in all states, to all groups, at one time. The necessary variation needed to be able to identify the model for previous expansions does not exist. 6 Elizabeth Richardson Vigdor and James Mercy explore the effects of state, but not federal, firearm laws on homicides in their 2003 and 2006 papers.

Elizabeth Richardson Vigdor and James Mercy explore the effects of state, but not federal, firearm laws on homicides in their 2003 and 2006 papers. 7 The Supreme Court's 7‐2 ruling in Hayes ( 2009

The Supreme Court's 7‐2 ruling in ( 8 While there are many other outcomes (felony assault, gunshot wounds, etc.) one might be interested in, these outcomes are not available in the form of national, public‐use data. Survey data are often unreliable, and the National Crime Victimization Survey is inappropriate as the data currently suppress the geocodes (these geocodes are not even available at a Census Research Data Center).

While there are many other outcomes (felony assault, gunshot wounds, etc.) one might be interested in, these outcomes are not available in the form of national, public‐use data. Survey data are often unreliable, and the National Crime Victimization Survey is inappropriate as the data currently suppress the geocodes (these geocodes are not even available at a Census Research Data Center). 9 All appendices are available at the end of this article as it appears in JPAM online. Go to the publisher's website and use the search engine to locate the article at http://onlinelibrary.wiley.com.

All appendices are available at the end of this article as it appears in JPAM online. Go to the publisher's website and use the search engine to locate the article at http://onlinelibrary.wiley.com. 10 I have no reason to suspect a state's reporting practices are correlated with the implementation of the GCA expansion. Prior to collecting data, states in the comparison and treatment groups were equally likely to have missing data. After collecting data, three states (DC, Illinois, and Kansas) remain missing. See Appendix available at the end of this article as it appears in JPAM online. Go to the publisher's website and use the search engine to locate the article at http://onlinelibrary.wiley.com.

I have no reason to suspect a state's reporting practices are correlated with the implementation of the GCA expansion. Prior to collecting data, states in the comparison and treatment groups were equally likely to have missing data. After collecting data, three states (DC, Illinois, and Kansas) remain missing. See Appendix available at the end of this article as it appears in JPAM online. Go to the publisher's website and use the search engine to locate the article at http://onlinelibrary.wiley.com. 11 Domestic violence and child abuse cases are notoriously difficult to prosecute and felony charges may be pled down to a misdemeanor for several reasons.

Domestic violence and child abuse cases are notoriously difficult to prosecute and felony charges may be pled down to a misdemeanor for several reasons. 12 Throughout the time series, felons were prohibited from possessing a firearm.

Throughout the time series, felons were prohibited from possessing a firearm. 13 I will describe the effects of the legal decisions as they pertain to the research design. Readers interested in the legal reasoning for what follows are encouraged to consult Supreme Court Chief Justice Robert's dissenting opinion in United States v. Hayes ( 2009

I will describe the effects of the legal decisions as they pertain to the research design. Readers interested in the legal reasoning for what follows are encouraged to consult Supreme Court Chief Justice Robert's dissenting opinion in ( 14 There are 12 circuit courts, a Federal Circuit, and a Court of Appeals for the Armed Forces in the United States. Eleven of the 12 circuit courts preside over multiple states, and DC has its own circuit court. Whenever a circuit court makes a ruling concerning federal law, all courts in its jurisdiction, which will span multiple states, are bound to follow its decision unless there is an appeal to the United States Supreme Court.

There are 12 circuit courts, a Federal Circuit, and a Court of Appeals for the Armed Forces in the United States. Eleven of the 12 circuit courts preside over multiple states, and DC has its own circuit court. Whenever a circuit court makes a ruling concerning federal law, all courts in its jurisdiction, which will span multiple states, are bound to follow its decision unless there is an appeal to the United States Supreme Court. 15 As a robustness check, I re‐run the analysis including these states; the results do not differ in any meaningful way.

As a robustness check, I re‐run the analysis including these states; the results do not differ in any meaningful way. 16 The number of denials issued by the FBI and the reasons for those denials is made available in the annual NICS Operations Report. The total number of denials by states is also provided, but the reason for denial is not included. In order to obtain the number of total national denials, I assume the percent of domestic denials is the same for both the FBI and state agencies. I then sum the annual totals to obtain the number over this time period.

The number of denials issued by the FBI and the reasons for those denials is made available in the annual NICS Operations Report. The total number of denials by states is also provided, but the reason for denial is not included. In order to obtain the number of total national denials, I assume the percent of domestic denials is the same for both the FBI and state agencies. I then sum the annual totals to obtain the number over this time period. 17 If a person is convicted of violating the GCA, they are subject to a federal felony conviction, a fine not to exceed $250,000, a maximum prison term of 10 years, or any combination of the above. (18 U.S.C. s 922(a)(2), 1994.) These penalties may be in addition to any state penalties for any additional crimes that may have been committed (e.g., if a convicted batterer commits a fresh assault and a gun is found in their possession at the time of arrest, they may be charged with assault under the state statute and possession of a weapon under the federal statute).

If a person is convicted of violating the GCA, they are subject to a federal felony conviction, a fine not to exceed $250,000, a maximum prison term of 10 years, or any combination of the above. (18 U.S.C. s 922(a)(2), 1994.) These penalties may be in addition to any state penalties for any additional crimes that may have been committed (e.g., if a convicted batterer commits a fresh assault and a gun is found in their possession at the time of arrest, they may be charged with assault under the state statute and possession of a weapon under the federal statute). 18 All appendices are available at the end of this article as it appears in JPAM online. Go to the publisher's website and use the search engine to locate the article at http://onlinelibrary.wiley.com.

All appendices are available at the end of this article as it appears in JPAM online. Go to the publisher's website and use the search engine to locate the article at http://onlinelibrary.wiley.com. 19 All appendices are available at the end of this article as it appears in JPAM online. Go to the publisher's website and use the search engine to locate the article at http://onlinelibrary.wiley.com.

All appendices are available at the end of this article as it appears in JPAM online. Go to the publisher's website and use the search engine to locate the article at http://onlinelibrary.wiley.com. 20 The FBI designates a person as the primary victim if they are listed first among the victims. The FBI does not provide any guidance to law enforcement agencies as to whom should be listed first; moreover, it is possible that law enforcement agencies do not even realize the distinction between primary and additional victims exists.

The FBI designates a person as the primary victim if they are listed first among the victims. The FBI does not provide any guidance to law enforcement agencies as to whom should be listed first; moreover, it is possible that law enforcement agencies do not even realize the distinction between primary and additional victims exists. 21 As an example of an assumption, if one observation in the data set involves a man killing his wife and there is another victim that is a young child, I assume the victim is the man's child or stepchild.

As an example of an assumption, if one observation in the data set involves a man killing his wife and there is another victim that is a young child, I assume the victim is the man's child or stepchild. 22 All appendices are available at the end of this article as it appears in JPAM online. Go to the publisher's website and use the search engine to locate the article at http://onlinelibrary.wiley.com.

All appendices are available at the end of this article as it appears in JPAM online. Go to the publisher's website and use the search engine to locate the article at http://onlinelibrary.wiley.com. 23 All appendices are available at the end of this article as it appears in JPAM online. Go to the publisher's website and use the search engine to locate the article at http://onlinelibrary.wiley.com.

All appendices are available at the end of this article as it appears in JPAM online. Go to the publisher's website and use the search engine to locate the article at http://onlinelibrary.wiley.com. 24 States implemented the expansion at various points in the calendar year, and the first year is weighted appropriately. For example, when a state implemented the expansion in July, the first year is given a weight of 0.5 rather than 1.

States implemented the expansion at various points in the calendar year, and the first year is weighted appropriately. For example, when a state implemented the expansion in July, the first year is given a weight of 0.5 rather than 1. 25 The states in the Second Circuit (Connecticut, New York, Vermont) are an exception. This decision was made on December 31, 2002. Therefore, the policy variable turns on in 2003.

The states in the Second Circuit (Connecticut, New York, Vermont) are an exception. This decision was made on December 31, 2002. Therefore, the policy variable turns on in 2003. 26 I run separate regressions where I include these states. This decision does not affect the results.

I run separate regressions where I include these states. This decision does not affect the results. 27 Other measures of violent crime, such as Aggravated Assaults, might have been preferable, but the FBI does not report statistics in a way that allows researchers to separate nondomestic and domestic crimes.

Other measures of violent crime, such as Aggravated Assaults, might have been preferable, but the FBI does not report statistics in a way that allows researchers to separate nondomestic and domestic crimes. 28 Prior to granting an Order of Protection, many states allow a potential victim to receive an “ex‐parte” (temporary) Order of Protection. Some states allow a judge to prohibit the perpetrator from possessing firearms during this period.

Prior to granting an Order of Protection, many states allow a potential victim to receive an “ex‐parte” (temporary) Order of Protection. Some states allow a judge to prohibit the perpetrator from possessing firearms during this period. 29 All appendices are available at the end of this article as it appears in JPAM online. Go to the publisher's website and use the search engine to locate the article at http://onlinelibrary.wiley.com.

All appendices are available at the end of this article as it appears in JPAM online. Go to the publisher's website and use the search engine to locate the article at http://onlinelibrary.wiley.com. 30 As a robustness check, I also used more aggregate denominators (e.g., all adults for intimate partners and all children for domestic children). Use of the more refined denominator does not change the magnitude of the DD coefficient, but it does add modest precision to the results.

As a robustness check, I also used more aggregate denominators (e.g., all adults for intimate partners and all children for domestic children). Use of the more refined denominator does not change the magnitude of the DD coefficient, but it does add modest precision to the results. 31 All appendices are available at the end of this article as it appears in JPAM online. Go to the publisher's website and use the search engine to locate the article at http://onlinelibrary.wiley.com.

All appendices are available at the end of this article as it appears in JPAM online. Go to the publisher's website and use the search engine to locate the article at http://onlinelibrary.wiley.com. 32 Gun homicide rates are not shown, but these trends follow the same pattern as overall homicide trends. If shown, the reader would note a downward shift of about 0.4 in the level of gun rates relative to overall homicide rates.

Gun homicide rates are not shown, but these trends follow the same pattern as overall homicide trends. If shown, the reader would note a downward shift of about 0.4 in the level of gun rates relative to overall homicide rates. 33 Two estimation techniques are frequently used in research using FBI homicide data: WLS (or OLS) regression where the dependent variable is a rate or a negative binomial regression where the dependent variable is a count. I use WLS. Guo and Trivedi ( 2002

Two estimation techniques are frequently used in research using FBI homicide data: WLS (or OLS) regression where the dependent variable is a rate or a negative binomial regression where the dependent variable is a count. I use WLS. Guo and Trivedi ( 34 After running Models 2 and 3 on each of the dependent variables, I tested the null hypothesis that trends were jointly equal to 0 (using postestimation techniques in Stata). The F ‐statistic was always large. In all instances I reject the null at the 0.01 level. This statistical evidence supports Model 3 as the preferred model.

After running Models 2 and 3 on each of the dependent variables, I tested the null hypothesis that trends were jointly equal to 0 (using postestimation techniques in Stata). The ‐statistic was always large. In all instances I reject the null at the 0.01 level. This statistical evidence supports Model 3 as the preferred model. 35 I also ran models with quadratic trends. This specification made no difference to the DD coefficient and the explanatory power of the model was also unaltered.

I also ran models with quadratic trends. This specification made no difference to the DD coefficient and the explanatory power of the model was also unaltered. 36 Whenever the term “rate” is used it refers to the rate per 100,000 persons in the population at risk.

Whenever the term “rate” is used it refers to the rate per 100,000 persons in the population at risk. 37 All percent changes are calculated by dividing the DD estimate by the weighted average of the model's dependent variable (gun or nongun homicide rate).

All percent changes are calculated by dividing the DD estimate by the weighted average of the model's dependent variable (gun or nongun homicide rate). 38 Though it is feasible the GCA expansion may also have an effect on nondomestic homicides if those that commit domestic homicides are also likely to commit nondomestic homicide. A JPAM Point/Counterpoint (Buzawa & Buzawa, 2013a 2013b 2013a 2013b

Though it is feasible the GCA expansion may also have an effect on nondomestic homicides if those that commit domestic homicides are also likely to commit nondomestic homicide. A JPAM Point/Counterpoint (Buzawa & Buzawa, 39 I also regressed state property crimes on the GCA expansion and found no relationship between the expansion and these crimes.

I also regressed state property crimes on the GCA expansion and found no relationship between the expansion and these crimes. 40 All appendices are available at the end of this article as it appears in JPAM online. Go to the publisher's website and use the search engine to locate the article at http://onlinelibrary.wiley.com.

All appendices are available at the end of this article as it appears in JPAM online. Go to the publisher's website and use the search engine to locate the article at http://onlinelibrary.wiley.com. 41 While none of the preperiod coefficients are significant, a declining trend is noticeable. Therefore, I conduct two additional falsification tests. One follows Linden and Rockoff ( 2008

While none of the preperiod coefficients are significant, a declining trend is noticeable. Therefore, I conduct two additional falsification tests. One follows Linden and Rockoff ( 42 At the request of a reviewer, I also conducted a test where I fully saturated the preperiod (a variable for if the law had been available four or more years but not fewer, available for three years but not fewer, available for two years but not fewer, and available for one year) and included an immediate policy effect variable (policy available for one year). The coefficients on the preperiod coefficients were positive but not significant.

Appendix If the panel were balanced, there would be 50 states plus DC over 29 years. Therefore, there would be a total of 1,479 state‐year observations. Due to missing homicide count data (used to construct the dependent variable), there are 1,325 state‐year homicide counts. I am able to obtain data from state law enforcement agencies for 56 state‐year observations, yielding a sample of 1,381. I remove an additional five states due to endogeneity concerns, and this yields a final sample size of 1,236. The problem of missing data arises because states are not required to report their annual homicide data to the FBI. If a state does not report data, the FBI has no way of including these numbers in their national data set (the FBI Supplementary Homicide Reports). I do not know why some states opt out of reporting, but there is no reason to believe a state's choice to report is in any way correlated to the federal gun ban. In an attempt to use data that was as complete as possible, I reached out to states that were either missing data in a given year or where the data was indicated inconsistent reporting. Some states were able to supply me with data that was completely compatible with the SHR data. Other states were able to provide useful but incomplete information, while other states were unable to assist me. Table A1. Missing and requested homicide data (1980 to 2008) States missing data Years missing Sample size reduction Alabama 1999 1 District of Columbia 1996, 1998 to 2008 29 Florida 1988 to 1991, 1996 to 2008 29 Illinois All years are unreliable. 29 Iowa 1991 1 Kansas 1993 to 1999 29 Kentucky 1988 1 Maine 1991 to 1993 3 Montana 1982, 1986, 1987, 1990, 1993, 1994, 1996 29 New Hampshire 1997 1 New Mexico 1981 1 Wisconsin 1998 1 Potential sample size reduction 154 Obtained data from Years added Sample size increase Alabama 1999 1 Florida 1996 to 2008 25 Maine 1991 to 1993 3 Montana 1993, 1994, 1996 25 New Hampshire 1997 1 Wisconsin 1998 1 Increases sample size by 56 Missing data reduced sample by 98 Sample after missing data is accounted For 1,381 Remove five additional states due to endogeneity 145 Final analytic sample size 1,236 Figure A1 Open in figure viewerPowerPoint Homicide Rate Trends before and after the Gun Control Act Expansion of 1996: Treated States. Notes: All rates are weighted by the state's annual population. Trend lines are limited to the treated states. Figure A2 Open in figure viewerPowerPoint Homicide Rate Trends before and after the Gun Control Act Expansion of 1996: Comparison States. Notes: All rates are weighted by the state's annual population. Trend lines are limited to the comparison states. Year since change is based off the year of the federal GCA Expansion (1996). Table A2. Descriptive statistics of independent variables used in analysis (1980 to 2008) All states States treated with GCA expansion Comparison states Average Standard deviation Average Standard deviation Average Standard deviation t‐Test of expansion states = comparison states Gun Ban 0.3281 0.4697 0.4040 0.4909 — — — Proportion white 0.8435 0.0841 0.8448 0.0850 0.8379 0.0803 0.2873 Proportion other race 0.0508 0.0617 0.0550 0.0669 0.0325 0.0227 0.0000 Proportion African American 0.1057 0.0729 0.1002 0.0727 0.1296 0.0686 0.0000 Proportion married 0.4487 0.0255 0.4457 0.0254 0.4618 0.0217 0.0000 Proportion divorced 0.0611 0.0130 0.0626 0.0127 0.0546 0.0122 0.0000 Proportion widowed 0.0497 0.0115 0.0482 0.0112 0.0561 0.0105 0.0000 Proportion single 0.4406 0.0319 0.4436 0.0324 0.4275 0.0257 0.0000 Poverty rate 14.04 3.76 14.60 3.70 11.62 2.93 0.0000 Household income (1996 Dollars, in 1,000s) 50.41 8.65 49.80 8.09 53.04 10.33 0.0000 Female:male employment ratio 0.8702 0.0731 0.8653 0.0737 0.8914 0.0666 0.0000 AFDC maximum (family of three; 1996 Dollars) 444.86 186.63 451.01 196.36 418.26 133.99 0.0234 Property crime rate (per 1,000) 4,277.17 1,229.91 4,439.41 1,234.39 3,575.75 929.16 0.0000 Robbery crime rate (per 1,000) 192.40 116.75 196.76 123.24 173.53 80.55 0.0102 Federal prosecutor initiates GCA charge 0.0821 0.2746 0.1011 0.3016 — — — Both gun laws apply 0.0149 0.1211 0.0183 0.1342 — — — State gun law 0.1860 0.3893 0.1948 0.3963 0.1480 0.3560 0.1190 Death penalty 0.8286 0.3770 0.8172 0.3867 0.8781 0.3280 0.0363 Unilateral divorce 0.9016 0.2979 0.8843 0.3201 0.9768 0.1508 0.0001 DV assault law 0.2854 0.4518 0.3514 0.4776 — — — OP gun clause 0.3452 0.4756 0.3333 0.4716 0.3968 0.4904 0.0823 Ex‐parte gun clause 0.2225 0.4161 0.2360 0.4249 0.1640 0.3712 0.0248 Observations 1,236 1,034 202 Table A3. Assessing the presence of policy leads and lags (1980 to 2008) Intimates Female intimates Male intimates Domestic children Female domestic children Male domestic children Five and six years −0.0311 0.0394 −0.1060** 0.0616*** 0.0347 0.0908*** PRE (0.0355) (0.0437) (0.0521) (0.0153) (0.0228) (0.0224) Three and four −0.0224 0.0565 −0.106 0.00953 −0.0021 0.0205 years PRE (0.0505) (0.0617) (0.0636) (0.0231) (0.0321) (0.0261) One and two years −0.0561 −0.0056 −0.1100 0.0176 0.0187 0.0185 PRE (0.0625) (0.0757) (0.0736) (0.0261) (0.0318) (0.0371) Year of and one −0.0859 −0.0541 −0.1210 −0.0154 0.0175 −0.0456 year POST (0.0718) (0.0797) (0.0883) (0.0228) (0.0353) (0.0371) Two and three −0.108 −0.0992 −0.1190 0.00809 0.0184 −0.0001 years POST (0.0760) (0.0847) (0.0928) (0.0293) (0.0386) (0.0410) Four and five years −0.1200 −0.1140 −0.1270 0.0038 0.0318 −0.0203 POST (0.0970) (0.107) (0.1180) (0.0338) (0.0487) (0.0465) Six or more years −0.0884 −0.1260 −0.0515 0.0171 0.0526 −0.0128 POST (0.1030) (0.1200) (0.1260) (0.0454) (0.0639) (0.0638) R2 0.812 0.812 0.870 0.476 0.231 0.467 Sample size 1,236 1,236 1,236 1,236 1,236 1,236 Randomly Assigning Enactment Dates to GCA Expansion among the Treated States One falsification test discussd in the paper involved randomly “turning on” the GCA Expansion policy variable and estimating the policy's effect on the subgroups (female intimates, female domestic children, etc.) mentioned in the analysis. In order to execute this test, I used Stata and conducted the following steps: Treated states were given a random GCA expansion enactment year. The random enactment year falls anywhere between 1980 and 2008—the complete span of years in my data set. The random year was chosen from a random uniform distribution. I constructed a new difference‐in‐difference (DD) variable using the random enactment years instead of the true enactment years used in the paper's analysis. I ran regressions using my preferred specification (Model 3 weighted by the state's population size) but substituted the new, randomly constructed DD variable. After running the regression, I stored this new DD estimate of the policy's effect. I generated 1,000 DD estimates using random policy enactment years for the eight outcomes in the paper (gun and nongun homicide rates for the four subgroups of interest). Assessing the Results I looked at the mean of the DD estimates in the distributions. The DD estimates’ distribution means should be centered at 0. On average, random laws should not have an effect on gun or nongun homicide rates. I then evaluated the null hypothesis that the effect of the GCA Expansion was 0 for the eight outcomes in the paper. Table A4 shows the mean of the randomly generated DD estimates, the standard error of the distribution, the DD estimates from the paper obtained using actual enactment dates, and the P value showing the likelihood that we would observe the effect found in the paper if the true effect was actually the mean generated by the simulation, which is always very near to 0. I also constructed graphs using a smoothed kernel density plot of the distribution of the DD estimates across the 1,000 simulations. The vertical lines represent the DD effect reported in the paper. Conclusion The analyses reported in the paper point to a statistically significant decline in gun homicide rates among female intimate partners and male domestic children. The exercise of randomly assigning enactment years supports this conclusion. If the true effect of the policy were 0, one would very rarely (less than 1 percent of the time) observe a 17.28 percent decline of female intimate gun homicide rates or a 30.92 percent decline of male domestic children gun homicide rates. The DD estimates among the other outcomes appear to be within sampling error, which also supports the paper's findings. Coding Rules for Imputing Victim Relationship When the primary victim was an intimate partner (WI, HU, XW, XH, GF, BF), I coded the additional victim as the child of the perpetrator if the additional victim was at least 16 years younger than the offender. When the primary victim was the child of the perpetrator (SO, SS, DA, SD), I coded the additional victim as also being the child of the perpetrator if the age between the primary and secondary was within 10 years of the primary victim. When the primary victim was the child of the perpetrator (SO, SS, DA, SD), I coded the additional victim as being the spouse of the perpetrator if the additional victim was 16 or more years older than the child victim, if the age difference between the primary victim and the perpetrator did not exceed 16 years, and if the additional victim and perpetrator were of the opposite sex. Figure A3 Open in figure viewerPowerPoint Distributions of Difference‐in‐Difference Estimates. A total of 1,000 Simulations Using Random GCA Expansion Enactment Dates, Vertical, Red Line is Actual DD Estimate Found in Paper. Table A4. Comparing random DD estimates to actual DD estimate found in paper Outcome Distribution mean of randomly generated DD estimates SE of randomly generated DD estimates DD estimate from actual enactment date (from paper) P value from a two‐tailed hypothesis test Female intimate partner gun homicide rate 0.0003 0.0376 −0.1360 <0.01 Male intimate partner gun homicide rate 0.0002 0.0635 0.0053 0.93 Female domestic children gun homicide rate −0.0005 0.0150 −0.0113 0.47 Male domestic children gun homicide rate −0.0000 0.0214 −0.0586 <0.01 Female intimate partner nongun homicide rate −0.0008 0.02191 −0.0053 0.98 Male intimate partner nongun homicide rate 0.0004 0.02005 0.0037 0.87 Female domestic children nongun homicide rate 0.0002 0.0390 −0.0062 0.87 Male domestic children nongun homicide rate −0.0011 0.0423 −0.0476 0.27 Population at Risk Formulas Federally defined domestic violence relationships (includes all current or former spouses, common‐law spouses, and all adult or minor children): Total population in a given state‐year observation. Intimate partners (includes all current or former spouses and common‐law spouses): Total population in a given state‐year observation × the proportion of CPS respondents identifying as married or divorced. Domestic children (includes all sons, stepsons, daughters, stepdaughters, or those similarly situated as a child): (proportion of victims in the FBI data that were 18 or under × State's 18 and under 18 population) + (proportion of victims in the FBI data that were over 18 × State's over 18 population). Analogous formulas were constructed to create female‐ and male‐specific risk populations.

Biography KERRI M. RAISSIAN is an Assistant Professor of Public Policy at the University of Connecticut, 1800 Asylum Avenue, 4th Floor, West Hartford, CT 06117 (e‐mail: kerri.raissian@uconn.edu).