Illustration by Kishjar via Flickr Crimes rates have plummeted in the U.S. since the mid-1990s.  Most of the credit for this remarkable trend has been given to an enlarged criminal justice system—largely more police, tougher sentencing and a massive prison complex. But we have found a larger and much more powerful explanation: A drop in interest rates and, in particular, long-term interest rates. When interest rates go up, crime goes up. When interest rates go down, crime goes down. This has bee...