Where Have All the Criminals Gone?

Freakonomics:

When the crime statistics for 2006 were released, the news media had no trouble declaring that the next big crime wave had hit (even though violent crime had just ticked up 2 percent, property crime fell by the same amount). So what’s happened since? Crime dropped across the country, especially in big cities. In the District of Columbia, once the nation’s murder capital, homicides are down 17 percent over last year. Big cities across the country are showing decreases in violent crime as well.