First of all, the level of firearm ownership in an area does have an effect on the firearm homicide rate. It correlates -
http://ajph.aphapublications.o...
Violent crime has gone down in most of the industrialized world over the past 3 decades, regardless of whether a country restricts firearms or not -
http://rgambler.com/2013/11/03...
http://jpo.wrlc.org/bitstream/...
http://www.economist.com/news/...
However, America's violent crime rate is much higher than most developed countries -
http://www.rawstory.com/rs/201...
http://en.wikipedia.org/wiki/C...
The growing consensus (in public policy circles at least) these days is that it is not gun ownership that is causing this violence, but the American gun culture -
http://www.businessweek.com/ar...
http://world.time.com/2012/12/...
http://www.cbc.ca/news/world/t...
The problem is that we keep looking at gun ownership rates The Swiss has high levels of gun ownership, but they also have a very strict culture of gun safety and training. Men are required to undergo military training and be in the reserves for 10 years, keeping their sealed army-issued firearm at home or in the Zeughaus, for use in case of invasion. Thus, they have lots of guns, but little gun crime.
Now, the question is how do you measure gun culture? In America you have this issues with two main groups poisoning the culture - the gangs and the "don't tread on me" types. How can you design a study to measure the effect of this culture on gun crime?