"This morning a lot of websites are touting a new study in Pediatrics that claims various forms of gun control reduce “pediatric” firearm deaths. By this the researchers mean deaths among all Americans aged 21 and under. (As I’ve pointed out before, also in the context of gun research in Pediatrics, even when you limit the age range to 18, you’re mainly talking about older teens, not young kids.)
Normally, if you want to know what effect a law has, you look to see what changed before and after it went into effect. Do states that enact the law experience different trends relative to states that don’t? This study doesn’t do that; though it combines five years’ worth of data, it just compares gun-death rates across states with various scores from the anti-gun Brady Campaign. It’s “cross-sectional,” in other words. It doesn’t tell us whether the laws actually do anything, or if states with fewer gun deaths are more likely to enact the laws to begin with."