Generally an income thing plus tighter gun laws.
Not sure what income has to do with guns. A gun can be bought for a couple hundred dollars. Those who want a gun will get one regardless of where they are. Canadians have easy access to the States and you certainly don't need to go through the waiting period for a purchase. Getting it over the boarder certinaly is no tough feet. There are Gun Shows all over this country and no waiting period is required for purchase from those shows (I have bought three this way myself ). Its all about availability. While many countries have strict guns laws, there are still guns there and those who believe tougher gun laws will eliminate guns are kidding themselves.