Advocates argue that gun control laws reduce the incidence of violent crimes by reducing the prevalence of firearms. Gun laws control the types of firearms that may be purchased, designate the qualifications of those who may purchase and own a firearm, and restrict the safe storage and use of firearms. On this view, fewer guns mean less crime. Thus, there is a two-step linkage between gun control and crime rates: (1) the impact of gun control on the availability and accessibility of firearms, particularly handguns, and (2) the effect of the prevalence of guns on the commission of crimes. The direction of the effect runs from gun control to crime rates.
Conversely, because high crime rates are often cited as justifying more stringent gun control laws, high rates may generate political support for gun regulations. This suggests a causal effect running from crime rates to more stringent gun laws. But because both relationships between gun control and crime rates unfold over time, they are not simultaneously determined in the usual econometric sense. For example, crime rates in the early 1990s could be expected, ceteris paribus, to influence the stringency of gun control measures in the late 1990s. In turn, more stringent gun control in the late 1990s could be expected, ceteris paribus, to affect crime rates several years later. Using state-level data, this article provides estimates of these twin relationships between gun control and crime rates.
Measuring the Degree of Gun Control
Researchers attempting to estimate the effect of gun control on crime rates face two problems. First, how is gun control to be measured? What is the empirical counterpart to gun control? Gun control is an umbrella term covering everything from laws prohibiting the ownership of defined classes of firearms to mandating the inclusion of gun locks with every firearm sold. These measures represent discrete legislative acts passed on different dates by different governing bodies. How do they interact to control the availability of firearms? Are the various measures complements or substitutes?
Second, the effectiveness of a particular gun control statute depends not only on its being on the books but the degree to which the law is enforced. Two jurisdictions may have the same gun control statute but experience very different effects, because in one of the jurisdictions little effort is devoted to enforcing the regulation. Enforcement of gun laws must be taken into account in order to accurately assess gun control.
One contribution of this study is that it addresses these problems by using a comprehensive index of gun control laws for the 50 states and the District of Columbia. The index includes those laws in place in 1998. Normalized to take on values of 0 to 100, the index is based on 30 weighted criteria applied to six categories of gun control regulations. The index was constructed as a project of the Open Society Institute's Center on Crime, Communities and Culture. (1) The index "concentrates on states because most gun laws are state laws, though federal law also plays an important role" (Open Society Institute 2000: 1). Because our study uses cross-sectional data by state, to match up with the index, federal laws are treated as a constant across all states and the District of Columbia. (2) Another reason for focusing on states is that 40 states prohibit or restrict local governments from enacting gun control ordinances.
Although there are literally thousands of state and local gun control statutes, the authors of the index group specific gun control measures into the following six categories. (1) Registration of firearms including purchase permits and gun registration of handguns and long guns (rifles and shotguns). (2) Safety training required before purchase. (3) Regulation of firearm sales including background checks, minimum age requirements for purchasing a firearm, a waiting period before a sale can be completed, one-gun-a-month limitation on purchases, all applied to long guns and/or handguns, plus a ban on "Saturday night specials," junk guns, and assault weapons. …