Key points are not available for this paper at this time.
Deborah Azrael, Lisa Hepburn, David Hemenway, Matthew Miller, The Stock and Flow of U.S. Firearms: Results from the 2015 National Firearms Survey, RSF: The Russell Sage Foundation Journal of the Social Sciences, Vol. 3, No. 5, The Underground Gun Market: Implications for Regulation and Enforcement (October 2017), pp. 38-57
Azrael et al. (Sun,) studied this question.