Question: Does anyone consider that this may be a bad test case? Not that I'm advocating or negating either gun control theory right now, but...
The test case here is a metropolitan city in the United States. There's not really an extensive border security issue there, allowing guns to be imported from neighboring states.
Remember, the argument in favor of gun control rests on the idea that we can eliminate guns entirely from a region. In a city that bans guns yet allows a relatively unchecked border, the statistics will be biased against the gun laws: it means there is little to prevent potential criminals from getting guns anyway, while only restricting those who do abide by the law.
To more accurately determine the effects of gun control, you would have to use a controlled environment: a city, state, or nation which made significant attempts to prevent guns from entering the region from outside.
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