A Rand Corporation review of studies of the effects of 18 policies designed to address mass killings... "found no qualifying studies showing that any of the 18 policies ... investigated decreased mass shootings.” To be clear, for nine of the policies (including red-flag laws and arming teachers), there were no studies that met Rand’s standards for quality and rigor. We don’t know the effects of those policies on the present crisis. It’s too soon to tell.
But nine policies were rigorously studied, and they include many of the most popular gun-control proposals in America, including background checks, bans on the sale of assault weapons and large-capacity magazines, minimum age requirements, and waiting periods. This finding is consistent with a famous fact-check by The Washington Post’s Glenn Kessler, where he found that neither enhanced background checks nor assault-weapons bans would have prevented recent, deadly mass shootings.
In 2015 Malcolm Gladwell wrote the single best, most insightful, and most sobering work yet written about mass shootings. The piece is complex, but the thesis is relatively simple—the United States is in the midst of something like a slow-motion riot, where each mass shooter is lowering the threshold for the next. The Columbine murders kicked off the “riot,” and we’ve been living with the consequences ever since.
Gladwell relied heavily on the work of Stanford sociologist Mark Granovetter, and Granovetter argues that it’s a mistake to view each incident on its own: In his view, a riot was not a collection of individuals, each of whom arrived independently at the decision to break windows. A riot was a social process, in which people did things in reaction to and in combination with those around them. Social processes are driven by our thresholds—which he defined as the number of people who need to be doing some activity before we agree to join them.