Researchers at Worcester State University, UMass Lowell, and Georgia State University scrutinized the backgrounds of individuals who perpetrated mass shootings during the period from 1990 to 2014. “Recalling that under the federal mental health background check law only persons who have been ‘adjudicated as a mental defective’ or ‘committed to any mental institution’ are prohibited from possessing firearms, we found that five public mass murderers” — 4.7 percent of the total — “would have had gun-disqualifying mental health records prior to their attacks.”
Silver, J. et al., “Public Mass Murderers and Federal Mental Health Background Checks for Firearm Purchases,” Law & Policy (forthcoming).
Is Canada next?
Maybe Canada should build a wall and make us pay for it. Not only did a poll taken right before Donald Trump’s election show that three-quarters of Canadians would consider voting for a candidate with Trump-like policies, but a study in the Canadian Journal of Political Science found that there’s been an increase in the partisan divide in that country with regard to inequality and welfare policy.
Kevins, A. & Soroka, S., “Growing Apart? Partisan Sorting in Canada, 1992–2015,” Canadian Journal of Political Science (March 2018).
Hold your fire
Using official and confidential data from “a large municipal police department in the Southwestern United States,” researchers compared incidents in which an officer fired his weapon versus incidents in which an officer drew his weapon but did not fire, controlling for the suspect’s race; the nature of the threat; the officer’s race, gender, years of experience, and recent complaints; and neighborhood crime and demographics. Black suspects, the researchers concluded, were about one third as likely to be shot as other suspects.
Worrall, J. et al., “Exploring Bias in Police Shooting Decisions with Real Shoot/Don’t Shoot Cases,” Crime & Delinquency (forthcoming).
Everyone I know is doing it
According to an analysis of polling data for both the US and French presidential elections, asking respondents how their acquaintances would vote was generally more effective at predicting the outcome than asking respondents about their own voting intentions. In fact, social-circle estimates were “more successful than both own-intention questions and aggregate polls in predicting winners of the five swing states that unexpectedly went to Trump (Florida, Michigan, North Carolina, Pennsylvania and Wisconsin). They predicted four of these states correctly, compared with three by own-intention questions and zero by aggregate polls.” And social-circle estimates showed a shift toward Trump in the weeks leading up to the election that was not revealed by own-intention questions.
Galesic, M. et al., “Asking about Social Circles Improves Election Predictions,” Nature Human Behaviour (March 2018).
Lend some green
Banks with branches in counties that experienced a fracking boom took in more deposits in those branches, which then allowed those banks to lend more in other counties. Using this natural variation in the availability of credit, a study found that greater availability of credit reduced pollution in these other counties as a whole and among firms that had relationships with those banks. These firms also earned better independent evaluations of environmental performance and were more likely to mention environmental protection in their annual reports. The theory is that extra credit helps finance pollution-control investments.
Levine, R. et al., “Bank Liquidity, Credit Supply, and the Environment,” National Bureau of Economic Research (March 2018).
Kevin Lewis is an Ideas columnist. He can be reached at email@example.com.