When tragedies happen, politicians aim to yell on the floors of Congress about how tragedies must be stopped. 

And gun tragedies should be entirely preventable, claim gun ban proponents. Just ban guns. It may make sense to assume that states in which there are tight laws make that state safer and lead to less gun crime, but that data show that the very opposite is true. You can't get a concealed weapon permit in Illinois but Chicago leads the US in gun murders. In 2013, a concealed carry bill was passed, making Illinois the final state to issue concealed gun carry permits.

Writing in Applied Economics Letters, Mark Gius from Quinnipac University finds that in states with more restrictive concealed carry weapons (CCW) laws there is actually an increase in gun related crime. Opponents always have an answer for data; criminals will get guns from other states and, in the case of Italy, where guns are banned but gun murders still happen, from other countries. But that essentially means the only people penalized for gun bans are law-abiding citizens.

Over the period of the analysis the average murder rate was 3.44 but states with more restrictive CCW laws had a gun-related murder rate that was 10% higher than the average. The Federal "assault weapons" ban had an even bigger impact, with murder rates 19.3% higher when this ban was in effect.

There are four broad types of CCW laws, unrestricted, which means an individual requires no permit to carry a concealed handgun. Shall issue, in which a permit is required but authorities must issue one to all qualified applicants that request one. May issue, in which authorities can deny a request for a permit and finally no issue, those states that do not allow private citizens to carry a concealed weapon.

There have been many conflicting studies on gun control but more limited research on assault weapon bans and CCW laws. Of those that do currently exist there has been a mix in the exact results, however, Lott and Mustard (1997) found those states with a less restrictive law saw a 7.65% drop in murders. The new study examines data from 1980 to 2009, one of the biggest time periods in research of this kind. It also looks solely at gun crime, rather than violent crime which is the case in similar research. State level data on gun related murder is taken from the Supplementary Homicide Reports from the United States Department of Justice and the information on CCW laws was obtained from a variety of United States bodies.

The conclusion was that limiting people’s ability to carry concealed weapons may cause murder rates to rise. 

Citation:  Mark Gius, 'An examination of the effects of concealed weapons laws and assault weapons bans on state-level murder rates', Applied Economics Letters DOI: 10.1080/13504851.2013.854294