40 Pages Posted: 8 Oct 2011 Last revised: 25 May 2013

Date Written: May 24, 2013

Abstract

This paper estimates the causal effect of police on traffic fatalities and injuries. Due to simultaneity, estimating the causal effect of police on crime is often difficult. We overcome this obstacle by focusing on a mass layoff of Oregon State Police in February of 2003, stemming from changes in property tax assessment in the prior decade. Due solely to budget cuts, 35 percent of the roadway troopers were laid off, which dramatically reduced citations. The subsequent decrease in enforcement is associated with a significant increase in injuries and fatalities, with the strongest effects under fair weather conditions outside of city-limits where state police employment levels are most relevant. The effects are similar using control groups chosen either geographically or through data-driven methods. Our estimates suggest that a highway fatality can be prevented with $309,000 of expenditures on state police.