But there have long been difficulties with the notion that unemployment causes crime. For one thing, the 1960s, a period of rising crime, had essentially the same unemployment rate as the late 1990s and early 2000s, a period when crime fell. And during the Great Depression, when unemployment hit 25%, the crime rate in many cities went down. Among the explanations offered for this puzzle is that unemployment and poverty were so common during the Great Depression that families became closer, devoted themselves to mutual support, and kept young people, who might be more inclined to criminal behavior, under constant adult supervision. These days, because many families are weaker and children are more independent, we would not see the same effect, so certain criminologists continue to suggest that a 1% increase in the unemployment rate should produce as much as a 2% increase in property-crime rates.

Yet when the recent recession struck, that didn't happen. As the national unemployment rate doubled from around 5% to nearly 10%, the property-crime rate, far from spiking, fell significantly. For 2009, the Federal Bureau of Investigation reported an 8% drop in the nationwide robbery rate and a 17% reduction in the auto-theft rate from the previous year. Big-city reports show the same thing. Between 2008 and 2010, New York City experienced a 4% decline in the robbery rate and a 10% fall in the burglary rate. Boston, Chicago and Los Angeles witnessed similar declines.

This is a fascinating read.