In a paper published in 2008, comparing highly regulated Californian gun shows with relatively unregulated Texas gun shows, there was no statistical difference in suicide rates, but the Texas shows, with far less regulation, showed a statistically significant drop in the homicide rate.
From the study:
"But our results provide little evidence of a gun show-induced increase in mortality in Texas. In fact, we find that in the two weeks following a gun show, the average number of gun homicides declines in the area surrounding the gun show. Aggregating across all gun shows in the state, we find that there are approximately 16 fewer gun homicides resulting from the 200 gun shows in the average year. In the sections below, we discuss several possible explanations for this counterintuitive finding. However, it is important to keep in mind that while these results are statistically significant, they are quite small – representing just one percent of all homicides in Texas in the average year."
This was not a small study. It included data for 10 years and 3,300 gun shows. The two states chosen, California and Texas, contain 20 percent of the population of the United States. It was not conducted by firearm freedom advocates or the NRA.
The evidence is clear. Stopping private sales at guns shows costs lives. President Obama's demand that all private sales be approved of by state agents before they can be made, is counterproductive and will cost innocent lives.
If this seems counterintuitive to you, consider that there is considerable evidence that more guns result in less crime. The logic to support this is not unreasonable. It is that criminals often make rational decisions based on their understanding of the environment that they are in. If they believe that their intended victim may be armed, they will often chose another target, decide not to commit the crime, or decide to commit a non-confrontational crime such as theft from an unoccupied vehicle.
When criminals notice that a gun show is being held in an area, and people can more easily buy and sell guns, it is reasonable to believe that they would understand that potential victims could be armed. This belief would then result in less homicides.
The important thing about this study is that it shows a statistically significant drop in homicides while there is no statistical difference in suicides.
The statistical significance shows that this is not a random artifact of the data gathering process, but is a real effect.
The study shows that requiring universal background checks, in Texas alone, would cost 16 lives per year.
I have been told the above link is to a draft. Here is a link to the final paper.