For decades, Missouri required a permit to purchase a handgun, even from a private seller. (Under federal law, licensed dealers must conduct background checks but private sellers don't have to.) In 2007 the law was repealed -- causing a rash of murders, according to a forthcoming study we featured in White Papers & Research today:

The study [from researchers with the Johns Hopkins Center for Gun Policy and Research], to be published in a forthcoming issue of Journal of Urban Health, finds that the law's repeal was associated with an additional 55 to 63 murders per year in Missouri between 2008 and 2012. State-level murder data for the time period 1999-2012 were collected and analyzed from the Federal Bureau of Investigation's (FBI) Uniform Crime Reporting (UCR) system. The analyses controlled for changes in policing, incarceration, burglaries, unemployment, poverty, and other state laws adopted during the study period that could affect violent crime.

Though I'm sympathetic to universal background checks, I'm skeptical that they could cause an effect this big, especially when implemented in just a single state. But one thing is for sure: Something weird happened to Missouri's murder rate starting in 2008.

Here's some FBI data I pulled myself:

It's normal for crime stats to fluctuate here and there, but Missouri has had five straight years of abnormally high murder rates while the nation's rate has been declining.

The forthcoming study reports that states bordering Missouri didn't experience anything like this; in a similar exercise, I tried ranking all the states by murder rate as of 2006 (the year before the law's repeal) and then comparing Missouri with the two states that straddled it on the list. Illinois wasn't too far off and borders Missouri, so I included it too. I got a similar result -- starting in 2008, Missouri's rate was noticeably and consistently high:

The new study finds that the increase occurred only with firearm murders specifically, and similarly I found that it's not evident with property crime or the overall violent-crime rate. For both of those, Missouri became a bit worse relative to the nation as a whole over the last decade or two, but didn't experience anything abrupt in 2008:

It's still possible this is a fluke, of course, but this isn't a bad case. The state's murder rate indeed soared the year after a gun law changed, and there's no other obvious explanation.

Robert VerBruggen is editor of RealClearPolicy. Twitter: @RAVerBruggen