What Caused the Crime Decline? This podcast examines the Brennan Center's new report that explores one of the nation’s least understood recent phenomena – the dramatic decline in crime nationwide over the past two decades – and analyzes various theories for why it occurred, by reviewing more than 40 years of data from all 50 states and the 50 largest cities. It concludes that over-harsh criminal justice policies, particularly increased incarceration, which rose even more dramatically over the same period, were not the main drivers of the crime decline. In fact, the report finds that increased incarceration has been declining in its effectiveness as a crime control tactic for more than 30 years. Its effect on crime rates since 1990 has been limited, and has been non-existent since 2000.