Mark Kaplan, professor of social welfare, spoke to Yahoo News about deadly shootings happening in California and the rest of the country. The government spends only a small amount of money on firearm violence research, Kaplan said. “Quite often with prevention, we don’t know what’s been prevented. That’s the problem. Because we don’t really have good research,” he said. Kaplan also said strong gun laws in places such as California are undercut by illegal trafficking across state borders. “The idea of piecing together a patchwork of 50 states and coming up with a national policy is almost impossible in this country.  … The problem is state lines, and how do we minimize the flow of firearms into areas that have very strict firearm laws.” The Half Moon Bay Review also cited Kaplan’s research into the relationship between social inequity and gun violence, including his finding that “there is a strong correlation between homicide per million and income inequality.”