The point is you can ban anything you want. It is not effective as it does not prevent the violence it simply provides a conduit. They banned guns now it is knife violence that is the issue. Once they ban "pointy" knives it will be screwdriver violence or cricket bat violence that is the problem. Where does it end?
They are not addressing the root of the problem. They are treating a symptom.
Be careful what you wish for when you ask for numbers. The crime statistics are at 30yr lows in the US with no gun control.
http://www.ojp.usdoj.gov/bjs/glance/viort.htm
Here is a nice link from a Prof at Simon Fraser on the issue.
http://www.sfu.ca/~mauser/papers/saf/GCAW290702.doc.pdf