[WillPostForFood]

You can't say "but guns stayed the same and crime both increased and decreased at points, which means that guns don't affect crime".

I didn't say they don't affect crime, but if crime spikes, then drops then spikes, while gun ownership remains steady, then it is a piece of evidence that crime is largely driven by something other than the quantity of guns.

[StavrosK]

How? The fact that you can stop eating omelettes and still have the same amount of eggs in your fridge doesn't make you can make omelettes without eggs.