Police, Crime and the Problem of Weak Instruments: Revisiting the “More Police, Less Crime” Thesis

Tomislav V. Kovandzic, Mark E. Schaffer, Lynne M. Vieraitis, Erin A. Orrick, Alex R. Piquero

    Research output: Contribution to journalArticlepeer-review

    18 Citations (Scopus)
    1080 Downloads (Pure)

    Abstract

    Objectives. A key question in the general deterrence literature has been the extent to which the police reduce crime. Definitive answers to this statement, however, are difficult to come by because while more police may reduce crime, higher crime rates may also increase police levels, by triggering the hiring of more police. One way to help overcome this problem is through the use of instrumental variables (IV). Levitt, for example, has employed instrumental variables regression procedures, using mayoral and gubernatorial election cycles and firefighter hiring as instruments for police strength, to address the potential endogeneity of police levels in structural equations of crime due to simultaneity bias. Methods. We assess the validity and reliability of the instruments used by Levitt for police hiring using recently-developed specification tests for instruments. We apply these tests to both Levitt’s original panel dataset of 59 US cities covering the period 1970–1992 and an extended version of the panel with data through 2008. Results. Results indicate that election cycles and firefighter hiring are “weak instruments”—weak predictors of police growth that, if used as instruments in an IV estimation, are prone to result in an unreliable estimate of the impact of police levels on crime. Conclusions. Levitt’s preferred instruments for police levels—mayoral and gubernatorial election cycles and firefighter hiring—are weak instruments by current econometric standards and thus cannot be used to address the potential endogeneity of police in crime equations.
    Original languageEnglish
    Pages (from-to)133-158
    Number of pages26
    JournalJournal of Quantitative Criminology
    Volume32
    Issue number1
    Early online date2 Jun 2015
    DOIs
    Publication statusPublished - Mar 2016

    Keywords

    • Crime
    • Endogeneity
    • Instrumental variables
    • Police

    ASJC Scopus subject areas

    • Pathology and Forensic Medicine
    • Law

    Fingerprint

    Dive into the research topics of 'Police, Crime and the Problem of Weak Instruments: Revisiting the “More Police, Less Crime” Thesis'. Together they form a unique fingerprint.

    Cite this