Everybody calls on statistics, but can't quote specifics.

Senator Mike Lee, Utah-
"I don't think we're going to legislate our way out of the risk. To the contrary, there is abundant research suggesting that in cities where more people own guns, the crime rate, espacially the murder rate, goes down."
Canadian Press, January 9, 2011; Lee-Ann Goodman.

I think Senator Lee is correct, at least for the West, but I can't produce reliable statistics.