You might not now know it watching the news these days but violent crime in Los Angeles is down to around one fifth of what it was at its peak in 1992. Even more surprising is that this trend has actually accelerated since 2008 even though you would expect there to be more crime as more people lost their jobs.
Even better this trend holds true to most of the USA. Part of this is improved techniques employed by the police, some of it is also due to a demographic shift as we are growing older. Also the fact that we are having more immigration also generally leads to lowered crime rates. Yes, you read that right! Increased immigration can possible lead to lower crime rates (Although that relationship is by no means certain).
Now if we could only figure out that perhaps we shouldn't incarcerate such a ridiculous percentage of our population, I think we could really have something here! Did you know that the USA incarcerates 5 times higher percentage of its people than China or 20 times more than India. Said another way, the USA has 5% of the world population but 25% of the worlds inmates, and I don't think it is because Americans have a natural higher propensity to turn to a life of crime.