“The Trouble with Crime Statistics: It’s surprisingly hard to say what makes crime go up or down”

The title of this post is the title of this extended New Yorker piece authored by Matthew Hutson. I recommend the full piece, and here is an excerpt:

Given the high stakes of the question, it’s tempting to take sides: either legalizing pot leads to more crime or it doesn’t.  And yet the truth may be unknowable.  “We do not have a good mechanism in place for tracking why a person commits crime,” Timothy Tannenbaum, a sheriff’s lieutenant in Washington County, Oregon, told me.  “I’m not sure most of the data you seek is available.”  In an e-mail, the spokesman for Sheriff Joseph McDonald, of Plymouth, Massachusetts, cautioned that “it’s often hard to identify marijuana as either the cause or the deterrent for criminal conduct.” I brought all these responses to David Weisburd, a criminologist at George Mason University. “The sheriffs raise an important question,” Weisburd said.  In his view, marijuana’s effects on crime are likely to remain hazy; in fact, the effect of pretty much anything on crime is rarely crystal clear.

Certainly, we know a few things about what causes and prevents crime.  The “Handbook of Crime Correlates,” from 2009, a reference book compiled by three criminologists, lists more than a hundred demographic, economic, relational, institutional, cognitive, and biological risk factors; in aggregate, they suggest that young men in hard times find trouble.  A 2015 report from the Brennan Center for Justice identifies a dozen plausible explanations for the major decline in crime that unfolded across America from 1990 to 2010 — among them, more police officers, a decline in alcohol consumption, a stronger economy, and the adoption of CompStat, a statistics-based approach to managing police departments, pioneered by the N.Y.P.D.  But each of these factors can explain only a few per cent of the broader change.  After analyzing a hundred and sixty-nine criminology studies published from 1968 to 2005, Weisburd found that, on average, each study — despite combining many variables — could explain only a third of a given change in crime.  A 2018 report in the Annual Review of Criminology concluded that the findings in one out of ten crime studies couldn’t be replicated, and that another fifteen per cent were only partially replicable.

“The world is complicated,” Weisburd said.  Many people are sure that they know how to reduce crime.  They urge the adoption or repeal of laws based on that conviction.  But crime and crime statistics are more mysterious than they seem.