The website reference, if you look at it, clearly states the statistics are from City of Chicago Data Portal, among other sources like the police department. Sorry if the name offends you, but it is the source and accuracy of the data that is important, if you did not review the information because you were expecting to be offended, that is your own prejudice.  The website i think is meant to be offensive to prove how offensive stupidity is.
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and yes, I read up on Chicago,  its not just "claim" or a "notion" spread "by gun nuts" here, read it.
https://en.wikipedia.org/wiki/Gun_laws_in_Illinois
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Up until December of 2012, you could not carry a gun legally. those murder rates by PEOPLE with guns were happening with the prohibition in tact. and the argument that "All of the guns in Chicago have come from somewhere else" EXACTLY proves the point, that the criminals do not care about the law. the law only negatively impact honest humans, not the scum that prey on others.