Shooting down the "more guns, less crime" hypothesis.

AuthorAyres, Ian

INTRODUCTION I. THEORETICAL ISSUES CONCERNING THE EFFECT OF INCREASED CARRYING OF CONCEALED HANDGUNS II. EMPIRICAL ISSUES IN ESTIMATING THE EFFECT OF INCREASED CARRYING OF CONCEALED HANDGUNS A. Introducing Explanatory Variables into the Panel Data Model 1. Model specification 2. Control variables B. Comparing the Results Using the Zheng and Lott Controls C. Sensitivity of the Lott Results to Time Period and Inclusion of Demographic Controls D. Problems with Unequal Years of Data from Early and Late Adopters in the Pre-Post Comparison E. Problems with Endogenous State Adoption III. MOVING FROM THE STATE TO THE COUNTY DATA A. Lott's County Data Analysis for 1977-1992 1. The dummy variable model 2. Lott's trend (or spline) model 3. The hybrid model testing for main and trend effects B. Extending Lott's County Data Through 1997 C. Replicating Table 10 While Controlling for State Trends IV. ESTIMATING STATE-SPECIFIC PASSAGE EFFECTS V. SOME INTERPRETATIONS AND SPECULATIONS A. Illustrating a Methodology for Deriving State-Specific Predictions B. The Resulting State-Specific Predictions CONCLUSION APPENDIX I: CODING THE TIMING AND STATUS OF SHALL-ISSUE LAWS APPENDIX II: DATA SOURCES FIGURES FIGURE 1A: ROBBERY RATES FOR STATES BY PASSAGE OF SHALL ISSUE LAW, WEIGHTED BY STATE POPULATION (VERNICK'S CODING) FIGURE 1B: VIOLENT CRIME RATES FOR STATES BY PASSAGE OF SHALL ISSUE LAW, WEIGHTED BY STATE POPULATION (VERNICK'S CODING) FIGURE 1C: MURDER RATES FOR STATES BY PASSAGE OF SHALL ISSUE LAW, WEIGHTED BY STATE POPULATION (VERNICK'S CODING) FIGURE 1D: RAPE RATES FOR STATES BY PASSAGE OF SHALL ISSUE LAW, WEIGHTED BY STATE POPULATION (VERNICK'S CODING) FIGURE 1E: AGGRAVATED ASSAULT RATES FOR STATES BY PASSAGE OF SHALL ISSUE LAW, WEIGHTED BY STATE POPULATION (VERNICK'S CODING) FIGURE 1F: PROPERTY CRIME RATES FOR STATES BY PASSAGE OF SHALL ISSUE LAW, WEIGHTED BY STATE POPULATION (VERNICK'S CODING) FIGURE 2: HOW DIFFERENT MODELS ESTIMATE THE LAW'S EFFECT WHEN THE PATH OF CRIME IS AN INVERTED V FIGURE 3A: VIOLENT CRIME--NORMALIZED EFFECT BY YEAR RELATIVE TO ADOPTION (VERNICK'S CODING) FIGURE 3B: MURDER--NORMALIZED EFFECT BY YEAR RELATIVE TO ADOPTION (VERNICK'S CODING) FIGURE 3C: RAPE--NORMALIZED EFFECT BY YEAR RELATIVE TO ADOPTION (VERNICK'S CODING) FIGURE 3D: AGGRAVATED ASSAULT--NORMALIZED EFFECT BY YEAR RELATIVE TO ADOPTION (VERNICK'S CODING) FIGURE 3E: ROBBERY--NORMALIZED EFFECT BY YEAR RELATIVE TO ADOPTION (VERNICK'S CODING) FIGURE 3F: PROPERTY CRIME--NORMALIZED EFFECT BY YEAR RELATIVE TO ADOPTION (VERNICK'S CODING) FIGURE 3G: AUTO THEFT--NORMALIZED EFFECT BY YEAR RELATIVE TO ADOPTION (VERNICK'S CODING) FIGURE 3H: BURGLARY--NORMALIZED EFFECT BY YEAR RELATIVE TO ADOPTION (VERNICK'S CODING) FIGURE 3I: LARCENY--NORMALIZED EFFECT BY YEAR RELATIVE TO ADOPTION (VERNICK'S CODING) FIGURE 4: IMPACT OF SHALL-ISSUE LAW ON VIOLENT CRIME (JURISDICTION-SPECIFIC DUMMY MODEL WITH STATE TRENDS, COUNTY DATA) FIGURE 5: IMPACT OF SHALL-ISSUE LAW ON MURDER (JURISDICTION-SPECIFIC DUMMY MODEL WITH STATE TRENDS, COUNTY DATA) FIGURE 6: IMPACT OF SHALL-ISSUE LAW ON PROPERTY CRIME (JURISDICTION-SPECIFIC DUMMY MODEL WITH STATE TRENDS, COUNTY DATA) FIGURE 7: FIVE-YEAR ANNUALIZED AVERAGE DOLLAR IMPACT OF SHALL-ISSUE LAWS OVER ALL CRIME TYPES TABLES TABLE 1: THE ESTIMATED IMPACT OF SHALL ISSUE LAWS ON CRIME, STATE DATA, USING STATE AND YEAR EFFECTS ONLY (VERNICK'S CODING) TABLE 2A: THE ESTIMATED IMPACT OF SHALL ISSUE LAWS ON CRIME, ZHENG'S STATE DATA, 1977-1999 (VERNICK'S CODING) TABLE 2B: THE ESTIMATED IMPACT OF SHALL ISSUE LAWS ON CRIME CONTROLLING FOR STATE TRENDS, ZHENG'S STATE DATA, 1977-1999 (VERNICK'S CODING) TABLE 3A: THE ESTIMATED IMPACT OF SHALL ISSUE LAWS ON CRIME, STATE DATA, 1977-1999 (VERNICK'S CODING), USING INCARCERATION RATES TABLE 3B: THE ESTIMATED IMPACT OF SHALL ISSUE LAWS ON CRIME CONTROLLING FOR STATE TRENDS, STATE DATA, 1977-1999 (VERNICK'S CODING), USING INCARCERATION RATES TABLE 4A: THE ESTIMATED IMPACT OF SHALL ISSUE LAWS ON CRIME, STATE DATA, 1991-1999 (VERNICK'S CODING), USING INCARCERATION RATES TABLE 4B: THE ESTIMATED IMPACT OF SHALL ISSUE LAWS ON CRIME CONTROLLING FOR STATE TRENDS, STATE DATA, 1991-1999 (VERNICK'S CODING), USING INCARCERATION RATES TABLE 5A: THE ESTIMATED IMPACT OF SHALL ISSUE LAWS ON CRIME, STATE DATA, 1977-1999 (VERNICK'S CODING), USING INCARCERATION RATES, ADDING ON DEMOGRAPHIC CONTROLS TO DUMMY VARIABLE MODEL TABLE 5B: THE ESTIMATED IMPACT OF SHALL ISSUE LAWS ON CRIME CONTROLLING FOR STATE TRENDS, STATE DATA, 1977-1999 (VERNICK'S CODING), USING INCARCERATION RATES, ADDING ON DEMOGRAPHIC CONTROLS TO DUMMY VARIABLE MODEL TABLE 6A: THE ESTIMATED IMPACT OF SHALL ISSUE LAWS ON CRIME, STATE DATA, 1977-1999 (VERNICK'S CODING), USING INCARCERATION RATES, INCLUDING ONLY BLACK AND WHITE MALES OVER AGE 10 AS DEMOGRAPHIC CONTROLS TABLE 6B: THE ESTIMATED IMPACT OF SHALL ISSUE LAWS ON CRIME CONTROLLING FOR STATE TRENDS, STATE DATA, 1977-1999 (VERNICK'S CODING), USING INCARCERATION RATES, INCLUDING ONLY BLACK AND WHITE MALES OVER AGE 10 AS DEMOGRAPHIC CONTROLS TABLE 7: YEARS AND STATES INCLUDED IN THE 1977-1999 TIME PERIOD RELATIVE TO SHALL-ISSUE LAW ADOPTION, STATE DATA (VERNICK'S CODING OF THE SHALL-ISSUE DUMMY) TABLE 8A: THE ESTIMATED IMPACT OF SHALL-ISSUE LAWS ON CRIME, STATE DATA, 1977-1999 (VERNICK'S CODING), USING INCARCERATION RATES, ADDING IN DUMMIES FOR YEARS MORE THAN 8 YEARS BEFORE OR 3 YEARS AFTER SHALL-ISSUE LAW ADOPTION TABLE 8B: THE ESTIMATED IMPACT OF SHALL-ISSUE LAWS ON CRIME CONTROLLING FOR STATE TRENDS, STATE DATA, 1977-1999 (VERNICK'S CODING), USING INCARCERATION RATES, ADDING IN DUMMIES FOR YEARS MORE THAN 8 YEARS BEFORE OR 3 YEARS AFTER SHALL-ISSUE LAW ADOPTION TABLE 9: TWO-STAGE LEAST SQUARES ESTIMATES OF THE IMPACT OF SHALL-ISSUE LAWS, STATE DATA (LOTT'S CODING) TABLE 10: THE ESTIMATED IMPACT OF SHALL-ISSUE LAWS ON CRIME, COUNTY DATA (LOTT'S CODING) TABLE 11: THE ESTIMATED IMPACT OF SHALL-ISSUE LAWS ON CRIME CONTROLLING FOR STATE TRENDS COUNTY DATA (LOTT'S CODING) TABLE 12: THE JURISDICTION-SPECIFIC ESTIMATED IMPACT OF SHALL-ISSUE LAWS ON CRIME, DUMMY MODEL CONTROLLING FOR STATE TRENDS IN CRIME, COUNTY DATA (LOTT'S CODING) TABLE 13: THE JURISDICTION-SPECIFIC ANNUALIZED FIVE-YEAR IMPACT OF SHALL-ISSUE LAWS ON CRIME, LINEAR HYBRID MODEL CONTROLLING FOR STATE TRENDS IN CRIME, COUNTY DATA (LOTT'S CODING) TABLE 14: ESTIMATES OF DOLLAR IMPACT OF CRIME (IN MILLIONS OF DOLLARS*) BASED ON JURISDICTION-SPECIFIC ANNUALIZED FIVE-YEAR IMPACT, HYBRID MODEL WITH STATE TRENDS (LOTT'S CODING) TABLE 15: ESTIMATED TOTAL DOLLAR IMPACT OF 24 SHALL-ISSUE LAWS (IN MILLIONS OF DOLLARS) TABLE 16: EXPLAINING THE ESTIMATED PERCENTAGE IMPACT ON CRIME OF THE 24 SHALL-ISSUE JURISDICTIONS APPENDIX TABLE 1: DIFFERENCES IN CODING DATES OF PASSAGE OF SHALL-ISSUE LAWS APPENDIX TABLE 2A: AYRES AND DONOHUE'S EXPANDED LOTT DATASET: LIST OF VARIABLES AND SUMMARY STATISTICS APPENDIX TABLE 2B: ZHENG'S DATASET: LIST OF VARIABLES AND SUMMARY STATISTICS APPENDIX TABLE 3A: THE ESTIMATED IMPACT OF SHALL ISSUE LAWS ON CRIME, STATE DATA, 1977-1999 (LOTT'S CODING), USING INCARCERATION RATES (ANALOGOUS TO TABLE 3A, BUT WITH LOTT'S CODING) APPENDIX TABLE 3B: THE ESTIMATED IMPACT OF SHALL ISSUE LAWS ON CRIME CONTROLLING FOR STATE TRENDS, STATE DATA, 1977-1999 (LOTT'S CODING), USING INCARCERATION RATES (ANALOGOUS TO TABLE 3B, BUT WITH LOTT'S CODING) APPENDIX TABLE 4A: THE ESTIMATED IMPACT OF SHALL ISSUE LAWS ON CRIME, STATE DATA, 1991-1999 (LOTT'S CODING), USING INCARCERATION RATES (ANALOGOUS TO TABLE 4A, BUT WITH LOTT'S CODING) APPENDIX TABLE 4B: THE ESTIMATED IMPACT OF SHALL ISSUE LAWS ON CRIME CONTROLLING FOR STATE TRENDS, STATE DATA, 1991-1999 (LOTT'S CODING), USING INCARCERATION RATES (ANALOGOUS TO TABLE 4B, BUT WITH LOTT'S CODING APPENDIX TABLE 5A: THE ESTIMATED IMPACT OF SHALL-ISSUE LAWS ON CRIME, STATE DATA, 1977-1999 (LOTT'S CODING), USING INCARCERATION RATES, ADDING IN DUMMIES FOR YEARS MORE THAN 8 YEARS BEFORE OR 3 YEARS AFTER SHALL-ISSUE LAW ADOPTION (ANALOGOUS TO TABLE 5A, BUT WITH LOTT'S CODING) APPENDIX TABLE 5B: THE ESTIMATED IMPACT OF SHALL-ISSUE LAWS ON CRIME CONTROLLING FOR STATE TRENDS, STATE DATA, 1977-1999 (LOTT'S CODING), USING INCARCERATION RATES, ADDING IN DUMMIES FOR YEARS MORE THAN 8 YEARS BEFORE OR 3 YEARS AFTER SHALL-ISSUE LAW ADOPTION (ANALOGOUS TO TABLE 5B, BUT WITH LOTT'S CODING) APPENDIX TABLE 6: ESTIMATING THE EFFECT OF SHALL-ISSUE LAWS USING LOTT'S TIME TREND SPECIFICATION FOR SELECTED YEARS APPENDIX TABLE 7: THE ESTIMATED IMPACT OF SHALL ISSUE LAWS ON CRIME, JURISDICTION-SPECIFIC HYBRID MODEL WITH STATE TRENDS APPENDIX TABLE 8: PREDICTION RESULTS INTRODUCTION

In a remarkable paper published in 1997, John Lott and David Mustard managed to set the agenda for much subsequent dataset work on the impact of guns on crime in America by creating a massive dataset of crime across all U.S. counties from 1977 through 1992 and by amassing a powerful statistical argument that state laws enabling citizens to carry concealed handguns had reduced crime. (1) The initial paper was followed a year later by an even more comprehensive and sustained argument to the same effect in a book solely authored by John Lott entitled More Guns, Less Crime (now in its second edition). (2) The work by Lott and Mustard has triggered an unusually large set of academic responses, with talented scholars lining up on both sides of the debate (3) Indeed, a panel of the National Academy of Sciences has been convened to sort through the now large body of conflicting studies.

But in the world of affairs rather than ideas, it did not take long for the National Rifle Association (NRA) and politicians across the country to seize upon the work of Lott and Mustard to oppose efforts at gun control and advance the cause of greater freedom to carry guns. For example, in the same year that the initial article was published, Senator Larry Craig (R-Idaho) introduced The Personal Safety and Community Protection Act, which was designed to facilitate...

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