I mentioned LAPD chief Bill Bratton's successes at reducing crime in New York City in the 1990s and Los Angeles today. His success in New York are pretty well known -- in just 27 months on the job, he reduced the city's epic crime rates, which had been climbing for decades, by dramatic percentages. Felony crime was down 39 percent. Homicides had fallen 50 percent.

More importantly, Bratton engineered a full-scale shift within the NYPD about how police officers view their role. For years, they'd been seen as responders to crime -- the causes of crime were seen as completely out of their control.  They thought of themselves, in Bratton's words, as report-takers.

But Bratton helped the cops come to understand their integral role in preventing crime as well. It's that fundamental paradigm shift that has allowed the crime reductions Bratton oversaw in the early 1990s to continue to this day.

But I was even more impressed by some of the stats Bratton shared from Los Angeles, where he's been police chief since 2002.

In the six year's since Bratton took office:

--homicide is down 44 percent

--rapes are down 35 percent

--robberies are down 23 percent

--overall violent crime is down 49 percent

--gang homicides are down 57 percent

--overall gang crime is down 25 percent

If that's not proof that Bratton's data-based approach to reducing crime is an effective tool, then I don't know what is.