Guns and Crime

Abstract

1. IntroductionGuns make crime easier to commit. Armed criminals are more easily able to secure cooperation. Guns also make it easier to commit larger scale crimes, such as bank robbery. More guns, therefore, can increase the number of criminals and encourage current criminals to be more active. Also, more guns in homes can encourage burglary, since guns are valuable loot (Cook and Ludwig 2003).On the other hand, people also acquire and use guns for self-defense. Cook and Ludwig (1997) estimate that 14 million people carried firearms for protection during the year prior to the survey (p. 8) and used them defensively at least 500,000 times.1 Criminals typically do not want to confront armed victims. Wright and Rossi (1986) report that one-third of the career criminals they interviewed reported being scared off, shot at, wounded, or captured by an armed victim (p. 15). Because criminals often do not know whether a potential is armed, they may be deterred from committing any crime involving face to face contact. Thus, gun carrying by ordinary citizens can reduce crime even against those who are not armed (Lott and Mustard 1997; Lott 2001). So, do guns cause more or less crime?A number of studies have examined the relationship between gun availability and crime (e.g., Kleck and Patterson 1993; Duggan 2001; Cook and Ludwig 2003; see Kleck, 1997, pp. 215-61 for a review). This research encounters two difficult methodological issues: the simultaneity discussed above and the difficulty in measuring gun availability. We address the simultaneity issue using Granger causality tests and simultaneous equation models with valid identifying restrictions. Previous studies have addressed the problem of measuring gun levels by constructing proxy variables. We use a new measure of gun availability based on the General Social Survey, the only direct measure of gun prevalence.In the next section we outline a simultaneous equation model of crime, guns, and sanctions. In Section 3 we discuss the data and data problems associated with gun prevalence, and we describe the development of a new measure of guns. Section 4 describes the econometric methods employed in our analysis of various dynamic panel data models. The results of the analyses are reported in Section 5. Section 6 discusses the issue of possible attenuation bias due to errors in variables. Section 7 summarizes and concludes the article.2. TheoryWe assume that crime is a function of guns and sanctions. The theoretical signs on the partial derivatives are subject to some dispute. Guns could cause crime because as guns become more prevalent, more will fall into the hands of criminals through loss and theft (Cook and Ludwig 2003). More guns could also lead to an escalation of violence, making crime more likely and more serious (Duggan 2001). On the other hand, Lott and Mustard (1997) find that the passage of right-to-carry concealed weapons laws, which presumably increases the number of guns, both at home and in public, reduces crime. It is entirely possible that both arguments are correct, in which case the net effect of guns on crime could be positive, negative, or zero. Similarly, both arguments could be wrong and guns are completely independent of crime, yielding a zero coefficient on guns in the crime equation. Thus, the sign of the partial derivative of guns in the crime equation remains an empirical question. Crime can also cause ordinary citizens to acquire guns for self-defense. Thus we would expect that the partial derivative of crime in the gun equation is positive.Society attempts to control crime through the use of sanctions. The criminal justice system includes the police who investigate crime and make arrests, prosecutors and judges who try the accused and sentence the guilty, and prisons where convicted felons are incarcerated. It is generally recognized that prisons reduce crime due to a combination of incarceration and deterrent effects (e. …