Why Has Crime Declined in the U.S.? Cont'd
The falling crime rate since the early 1990s has a number of documented causes and even more correlations associated with it, forming a very inconclusive picture—as we illustrated yesterday. Soon after publishing that note, we received a tweet calling for a clarification on the second chart we posted, the one showing the breakdown of possible causes for falling crime since the year 2000:
@TheAtlNotes @TheAtlQ decrease in crack use has "likely no effect" because as a population crack users represent such small # of ppl?— Nate Eckman (@nathaneckman) September 28, 2015
It’s another great question. I reached out to Inimai Chettiar, whose team at the Brennan Center for Justice at the NYU School of Law gathered the existing evidence on falling crime since the ‘90s and created those two charts we posted. Chettiar, who authored that Atlantic piece from earlier this year, was kind enough to expand on the minor role of crack. Here she is via email:
Many believe, with reason, that the decline in crack cocaine use during the 1990s contributed to declining crime over the same period. Since strong data on drug use (and particularly crack use) can be challenging to obtain, our report relied on existing research for our conclusions on the relationship between crime and crack use.
Economists, including Steven Levitt, have argued that a direct correlation between declining crime and crack cocaine use existed in the 1990s. The theory is that since crack use is associated with violence, a decrease in crack use should lead to a decrease in violent crime and/or theft.
However, shrinking unemployment over the same period may have caused both lower crime and lower crack use, so it is difficult to assert a causal relationship between the two. This led us to conclude that declining crack use could have played a role in the decline in crime in the 1990s.
The picture in the 2000s is clearer. Crack cocaine use was relatively constant on a national level from 2000 to 2010. Because there was little change in the use of crack, we are able to conclude it likely did not play a role in falling crime rates during that period.
Here’s a more detailed overview of Levitt’s work on the crack question.