The graph above shows the evolution of the homicide rate with firearms in the United States (Source; right axis) and data on gun ownership based on the general social survey (source; left axis). I have adjusted the axes. The correlation is quite striking, but of course as always the causality relationship is unclear. On the one hand, one can argue that fewer guns around mean less opportunity for crime. On the other, fewer homicides may remove the need for people to purchase guns to protect themselves. In any case, this doesn’t show that more guns mean less crime. On the contrary.
Click to access GSS_Trends%20in%20Gun%20Ownership_US_1972-2014.pdf