Do More Police = Less Crime?

Does an increased number of police officers patrolling the streets equal less crime? Not necessarily, according to this report from the Civic Strategies E-letter. Here's an excerpt:
"Why was it hard to see the reverse correlation between cops and robbers before now? Because there's a difference between causation and coincidence. That is, if a city hires a lot of officers and the crime rate plummets, did the beefed-up police presence cause crime to decline or was it coincidence? And there are other explanations around for why crime rates rise and fall, from unemployment and cheap handguns to violence on television and a decline in morality. Wouldn't they explain at least some of the changes in crime?" Read more...