In 2003, Rhode Island unintentionally decriminalized indoor prostitution.

The state's legislature amended a law in 1980, believing that the law inadvertently outlawed some forms of consensual sex between adults. That amendment created a legal loophole — one that sat unnoticed until 2003, when a District Court judge interpreted it to mean that paying for consensual sex was not a criminal offense in Rhode Island, not if it took place privately indoors. It took the state until 2009 to close the loophole.

The state's little legal accident was a bit embarrassing. But it did have a silver lining: it could serve as a "natural experiment," allowing researchers to estimate causal effects of decriminalizing sex work.

In a new paper from the National Bureau of Economic Research, economists Scott Cunningham and Manisha Shahlook at the six years when residents knew prostitution in Rhode Island wasn't a crime. And they show evidence that Rhode Island's decriminalization caused a steep decline in both forcible rape offenses and the incidence of gonorrhea.

What happened when Rhode Island decriminalized indoor prostitution?

"Indoor" prostitution refers to sex work that takes place through massage parlors, escort agencies, and most of the online market, compared to outdoor street-based prostitution.

The authors found evidence that, after decriminaliztion, the size of the indoor sex market increased — as expected — and prices commensurately fell.

More surprising was the finding that forcible rape offenses fell by 31 percent in Rhode Island from 2004 to 2009, as decriminalized indoor sex work scaled up in the state. This translates to 824 fewer reported rapes. The majority