This puts to rest the notion that nothing works to reduce gun violence.

[flamin lib]

In Missouri, Fewer Gun Restrictions and More Gun Killings

In the past decade, Missouri has been a natural experiment in what happens when a state relaxes its gun control laws. For decades, it had one of the nation’s strongest measures to keep guns from dangerous people: a requirement that all handgun buyers get a gun permit by undergoing a background check in person at a sheriff’s office.
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But the legislature repealed that in 2007 and approved a flurry of other changes, including, last year, lowering the legal age to carry a concealed gun to 19.
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Research by Daniel Webster, the director of the Johns Hopkins Center for Gun Policy and Research, found that in the first six years after the state repealed the requirement for comprehensive background checks and purchase permits, the gun homicide rate was 16 percent higher than it was the six years before. During the same period, the national rate declined by 11 percent. After Professor Webster controlled for poverty and other factors that could influence the homicide rate, and took into account homicide rates in other states, the result was slightly higher, rising by 18 percent in Missouri.

http://www.nytimes.com/2015/12/22/health/in-missouri-fewer-gun-restrictions-and-more-gun-killings.html?_r=1

Excerpt from the study abstract:

In the USA, homicide is a leading cause of death for young males and a major cause of racial disparities in life expectancy for men. There are intense debate and little rigorous research on the effects of firearm sales regulation on homicides. This study estimates the impact of Missouri’s 2007 repeal of its permit-to-purchase (PTP) handgun law on states’ homicide rates and controls for changes in poverty, unemployment, crime, incarceration, policing levels, and other policies that could potentially affect homicides. Using death certificate data available through 2010, the repeal of Missouri’s PTP law was associated with an increase in annual firearm homicides rates of 1.09 per 100,000 (+23 %) but was unrelated to changes in non-firearm homicide rates. Using Uniform Crime Reporting data from police through 2012, the law’s repeal was associated with increased annual murders rates of 0.93 per 100,000 (+16 %). These estimated effects translate to increases of between 55 and 63 homicides per year in Missouri.