Gun control advocates argue that because sales at gun shows are much less regulated than other sales, such shows make it easier for potential criminals to obtain a gun. Similarly, one might be concerned that gun shows would exacerbate suicide rates by providing individuals considering suicide with a more lethal means of ending their lives.
On the other hand, proponents argue that gun shows are innocuous since potential criminals can acquire guns quite easily through other black market sales or theft.
…we use data from Gun and Knife Show Calendar combined with vital statistics data to examine the effect of gun shows. We find no evidence that gun shows lead to substantial increases in either gun homicides or suicides. In addition, tighter regulation of gun shows does not appear to reduce the number of firearms-related deaths.
That is evidence from Texas and California from Mark Duggan, Randi Hjalmarsson, and Brian Jacob. They take care to point out that their estimates are short term and localized.
I would have imagined the number of guns in the area are in equilibrium before the gun show. Does a gun show create a discontinuous change in the actual number of guns used?
Of course, questions like these might be answered if I had the time to carefully read all the papers I blog.