[StavrosK]

Your causation goes the wrong way. The GP didn't say that less crime would cause fewer guns, but that fewer guns would cause less crime. 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".

[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.