https://www.ojp.gov/ncjrs/virtual-library/abstracts/does-allowing-law-abiding-citizens-carry-concealed-handguns-save

The study used FBI annual cross-sectional time-series county crime data for all 3,054 U.S. counties from 1977 to 1992. Although many recent crime studies have used proxies for deterrence, such as police expenditures or general levels of imprisonment, this study used arrest rates by type of crime, and also, for a subset of data, conviction rates and sentence lengths by type of crime. The most conservative estimates show that the adoption of “shall issue” right-to-carry firearm laws reduced murders by 8 percent, rapes by 5 percent, aggravated assault by 7 percent, and robbery by 3 percent. Although the initial drop in crime was often small, the longer the law was in effect, the larger the drop in crime over time. The benefits of concealed handguns were not limited to those who used a handgun in self- defense. By virtue of the fact that handguns were concealed, criminals were unable to tell whether a potential victim was equipped to strike back, thus making it less attractive for criminals to commit crimes when they came into direct contact with victims. An additional woman carrying a concealed handgun reduced the murder rate for women by approximately three to four times more than an additional man carrying a concealed handgun reduced the murder rate for men. Further, the study found that the increased use of guns in heated traffic disputes and the increased number of accidental handgun deaths was insignificant compared to the lives saved from violent crime that was prevented.