Free market capitalism does increase wealth disparity, or does not decrease it, like Valg said. High wealth disparity causes some to be poor(the total wealth of the state is assumed as constant) and some rich, while in a country with low disparity you have lower middle class and upper middle class and not so many rich or poor people.

Personally, I think that poverty does increase crime rates, as poor people don't have so much to lose when taking a risk compared to middle-classed people.