In this paper, we examine the evolution of the impact of older scholarly articles. We attempt to answer four questions. First, how often are older articles cited and how has this changed over time. Second, how does the impact of older articles vary across different research fields. Third, is the change in the impact of older articles accelerating or slowing down. Fourth, are these trends different for much older articles. To answer these questions, we studied citations from articles published in 1990-2013. We computed the fraction of citations to older articles from articles published each year as the measure of impact. We considered articles that were published at least 10 years before the citing article as older articles. We computed these numbers for 261 subject categories and 9 broad areas of research. Finally, we repeated the computation for two other definitions of older articles, 15 years and older and 20 years and older. There are three conclusions from our study. First, the impact of older articles has grown substantially over 1990-2013. In 2013, 36 of citations were to articles that are at least 10 years old; this fraction has grown 28 since 1990. The fraction of older citations increased over 1990-2013 for 7 out of 9 broad areas and 231 out of 261 subject categories. Second, the increase over the second half (2002-2013) was double the increase in the first half (1990-2001). Third, the trend of a growing impact of older articles also holds for even older articles. In 2013, 21 of citations were to articles >= 15 years old with an increase of 30 since 1990 and 13 of citations were to articles >= 20 years old with an increase of 36 . Now that finding and reading relevant older articles is about as easy as finding and reading recently published articles, significant advances aren't getting lost on the shelves and are influencing work worldwide for years after.
Exploring the notion of obsolescence from a usage perspective, rather than a citation perspective, Sandison @cite_3 found that, after an initial period, the usage of older issues of Physics journals at MIT didn't decrease with age.
@cite_3
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Chen's data for the raw frequency of use of 138 physics journals in the science library at M I T are re‐examined and converted to densities of use‐per‐metre of shelf. Other units of size for obtaining densities, and their measurement, are discussed. There is no evidence for synchronous obsolescence in the 1955 to 1968 volumes of these journals: instead there is some statistically significant evidence of greater density of use with greater age. Similar evidence elsewhere is cited. The ranking order for heaviness of use is also radically altered by converting raw frequencies to densities of use. It is suggested that, for comparing the relative values of different journals, or age groups, in library use or citation studies, analyses of raw frequencies are valueless, and indeed potentially dangerously misleading, until they are converted to allow for the numbers of available items in each group examined. The article presents the early findings of an exploratory deep log analysis of journal usage on OhioLINK, conducted as part of the MaxData project, funded by the U.S. Institute of Museum and Library Services. OhioLINK, the original “Big Deal,” provides a single digital platform of nearly 6,000 full-text journals for more than 600,000 people; for the purposes of the analysis, the raw logs were obtained from OhioLINK for the period June 2004 to December 2004. During this period approximately 1,215,000 items were viewed on campus in October 2004 and 1,894,000 items viewed off campus between June and December 2004. This article provides an analysis of the age of material that users consulted. From a methodological point of view OhioLINK offered an attractive platform to conduct age of publication usage studies because it is one of the oldest e-journal libraries and thus offered a relatively long archive and stable platform to conduct the studies. The project sought to determine whether the subject, the search approach adopted, and the type of journal item viewed (contents page, abstract, full-text article, etc.) was a factor in regard to the age of articles used. © 2006 Wiley Periodicals, Inc. Historically, papers have been physically bound to the journal in which they were published; but in the digital age papers are available individually, no longer tied to their respective journals. Hence, papers now can be read and cited based on their own merits, independently of the journal's physical availability, reputation, or impact factor (IF). We compare the strength of the relationship between journals' IFs and the actual citations received by their respective papers from 1902 to 2009. Throughout most of the 20th century, papers' citation rates were increasingly linked to their respective journals' IFs. However, since 1990, the advent of the digital age, the relation between IFs and paper citations has been weakening. This began first in physics, a field that was quick to make the transition into the electronic domain. Furthermore, since 1990 the overall proportion of highly cited papers coming from highly cited journals has been decreasing and, of these highly cited papers, the proportion not coming from highly cited journals has been increasing. Should this pattern continue, it might bring an end to the use of the IF as a way to evaluate the quality of journals, papers, and researchers. © 2012 Wiley Periodicals, Inc. This article challenges recent research (Evans, 2008) reporting that the concentration of cited scientific literature increases with the online availability of articles and journals. Using Thomson Reuters' Web of Science, the present article analyses changes in the concentration of citations received (2- and 5-year citation windows) by papers published between 1900 and 2005. Three measures of concentration are used: the percentage of papers that received at least one citation (cited papers); the percentage of papers needed to account for 20 , 50 , and 80 of the citations; and the Herfindahl-Hirschman index (HHI). These measures are used for four broad disciplines: natural sciences and engineering, medical fields, social sciences, and the humanities. All these measures converge and show that, contrary to what was reported by Evans, the dispersion of citations is actually increasing. © 2009 Wiley Periodicals, Inc.