John R. Lott studied it and published the results, here's an interview with some questions: http://www.press.uchicago.edu/Misc/Chicago/493636.html
"Gun Control and Economic Discrimination" - Journal of Criminal Law and Criminology (Winter 1995)
http://www.washingtontimes.com/news/2010/jan/21/guns-decrease-murder-rates/
... it's not hard to find these...
Ok, so I click the first link, and I find myself in an interview. Ok then, lets see if we can find some real figures...
Nope, nothing. Nothing that would be thought of as a real study. A few numbers stand out, but I can't find where these numbers came from, thus they are worthless. How about a source? Can I find a source?
Well no, and as this is an interview, I wouldn't expect one, but it does cast a shadow of doubt over the usefulness of this page.
Now I'm suspicious of this page, and start to look for tell tail signs of bias. Oh look, on the left hand side of the page is an advert for a book, written by the guy being interviewed. I also can't see to find the name of the interviewer, leaving me to wonder how do I check to make sure it is a real interview?
Any sort of sceptical mind would dismiss this for lack of any merit at all. It is a propaganda site.
Okto the second link! Well look, a newpaper! Not exactly what I would have hoped for, but let's read it anyway to see if
they manage to reference any sort of real data. Remember, peoples opinions in newspapers does not make proof.
Well nope, no source. Heart breaking that I am subject to the filtered opinion of a newspaper instead of a real study, but I'm noticing some numbers! Will these be real figures, or just cherry picking to try and make it fit a point of view?
Hmm, it is giving me some base figures from two cities, Washington and Chicago. Do I really trust two cities to form a trend? Well no I do not. It also focuses on a very short time frame after a change in the law, rather than any larger study over many cities over more time. Sorry buddy, but this looks like cherry picking.
I'm dismissing both sites on the grounds on having zero credible scientific value. Can you do better?