Illegal drug markets and victimizing crime in New York

Abstract

It is an embarrassment to criminology that the causes of the great American crime drop are so poorly understood. The essay ‘‘More Drugs, Less Crime,’’ by Wendel et al. (2016) adds a new idea to the body of explanations that earlier theorists have proposed—that falling prices of illegal drugs reduced property crime and violent crime. Unique to the literature on the crime drop, Wendel et al. (hereafter WDCH) draw on both ethnographic study of New York’s market for illegal drugs, and an econometric analysis of quantitative time series data, in support of their thesis. Regrettably we do not have comparable ethnographic observations of victimizing crime in New York, to help specify the relationship between the sale and use of illegal drugs, and victimizing crime. The WDCH proposal is all the more intriguing because it is directly contradictory to some journalistic accounts linking recent crime spikes in St. Louis to conflicts among suppliers stemming from a drop in the price of heroin (Williams 2016). The statistical method WDCH use to relate drug prices to crime rates is Granger causality, sometimes known as ‘‘Granger (non)-causality.’’ When I read studies using this method, I often come away thinking that the authors want to have their econometric cake and eat it too. On the one hand, they remind us that Granger causality is not necessarily the same as ordinary causality. It tells us whether lagged values of a particular variable (call it x) contribute significantly to the explanation of a second variable, y, above and beyond what lagged values of y alone contribute. This is not sufficient to establish causality in the sense that statisticians use this term nowadays. Yet the analyses are undertaken in a context where the question of