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## Firearms and Violence: A Critical Review (2004) Committee on Law and Justice (CLAJ)

### Citation Manager

. "7 Firearms and Suicide." Firearms and Violence: A Critical Review. Washington, DC: The National Academies Press, 2004.

 Page 169

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Firearms and Violence: A Critical Review
 BOX 7-2 Monte Carlo Experiment There is not enough information available from the published Monte Carlo design (Miller et al., 2002a, 2002b) to enable someone to replicate it. However, the committee did a Monte Carlo experiment that implied quite different results. The Monte Carlo simulates a study of the relation between the suicide rate and FS/S as a proxy for gun ownership. Let Z1, Z2, and Z3 denote unobserved independent standard normal variables, and let FS = 10 + Z1; NFS = 6 + Z2; FS/S = FS/(FS + NFS); POP = 50 + Z3; and RATE = (FS +NFS)/POP, where FS is the number of firearm suicides, NFS is the number of nonfirearm suicides, POP is the population size, and RATE is the total suicide rate for the population. With 1,000 replications, this design gave a mean value of FS/S in the neighborhood of 0.6 (similar to the fraction of suicides currently committed with a firearm in the United States). The correlation coefficient of FS/S and RATE was –0.29. The linear regression of RATE on FS/S gave a slope coefficient of –0.18 with a t-statistic of 9.6. So, according to this simulation, there is a negative association between the suicide rate and FS/S. In other words, if FS/S is a good proxy for ownership, gun owners are less likely than nonowners to commit suicide.

obvious why the simulation is at all relevant: the basic finding that proxies create biases is an analytical result that cannot be resolved by a simulation. It is very easy to create other plausible simulations that lead to substantial correlations between FS/S and suicide and, more importantly, substantial biases in the estimated relations of interest.

In Box 7-2, for example, we present the results of a simulation conducted by the committee. In this Monte Carlo simulation, we study the relation between the suicide rate and FS/S as a proxy for gun ownership, but we derive very different results than those reported by Miller et al. (2002a, 2002c). In particular, we find a negative association between the suicide rate and FS/S: in this simulation, if FS/S is a good proxy for ownership, gun owners are less likely than nonowners to commit suicide.

This exercise illustrates at least two things: (1) the design of the Monte Carlo simulation matters and (2) having suicide-related variables on both sides of the regression can produce perverse results. In the end, the biases created by proxy measures are application specific. Duggan (2003), for example, highlights the potential problems caused by using FS/S as an explanatory variable in a model whose dependent variable is also suicide-related. As demonstrated in the simulation above, unobserved factors associated with

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 Front Matter (R1-R12) Executive Summary (1-10) 1 Introduction (11-18) 2 Data for Measuring Firearms Violence and Ownership (19-52) 3 Patterns of Firearm-Related Violence (53-71) 4 Interventions Aimed at Illegal Firearm Acquisition (72-101) 5 The Use of Firearms to Defend Against Criminals (102-119) 6 Right-to-Carry Laws (120-151) 7 Firearms and Suicide (152-200) 8 Firearm Injury Prevention Programs (201-220) 9 Criminal Justice Interventions to Reduce Firearm-Related Violence (221-241) References (242-268) Appendix A Dissent--James Q. Wilson (269-271) Appendix B Committee Response to Wilsonâ€™s Dissent (272-275) Appendix C Judicial Scrutiny of Challenged Gun Control Regulations: The Implications of an Individual Right Interpretation of the Second Amendment--Scott Gast (276-298) Appendix D Statistical Issues in the Evaluation of the Effects of Right-to-Carry Laws--Joel L. Horowitz (299-308) Appendix E Biographical Sketches of Committee Members and Staff (309-316) Index (317-328)