(JAMA Network) For this analysis, researchers examined monthly data on US background checks for gun purchases and permits from November 1998 through April 2016, and they looked for purchasing trends after mass shootings during that time. A total of 124 major mass shootings (five or more individuals injured or killed) and nearly 234 million background checks occurred.

Original source: https://www.eurekalert.org/pub_releases/2019-04/jn-cig040319.php