Amid a sharp economic downturn in 2008, police departments around the United States experienced budget shortfalls that required them to enact cutbacks. A new study examined the effects on crime of budget shortfalls in two New Jersey cities–one of which laid off more than 10 percent of its police force while the other averted layoffs. The study found that the police layoffs were associated with significant increases in overall crime, violent crime, and property crime.

The study, by researchers at John Jay College of Criminal Justice and Rutgers University, appears in Justice Evaluation Journal, a publication of the Academy of Criminal Justice Sciences.

“Our study suggests that sudden and drastic reductions in the size of a police force via layoffs of police officers can generate significant increases in crime,” explains Eric Piza, associate professor at John Jay College of Criminal Justice, who led the study. “In Newark, this meant approximately 110 additional violent crimes and 100 additional property crimes per month.”

The study examined New Jersey’s two largest police forces: the Newark Police Department, which released 13 percent of its police force on one day in 2010, and the Jersey City Police Department, which averted layoffs by reducing the amount of a previously requested raise and increasing the copay for medical prescriptions for officers. In addition, between 2012 to 2015, Newark’s police department lost officers to attrition and did not hire new personnel, while Jersey City’s department added more officers.

Prior studies on the effect of decreases in the size of police forces on crime have considered incremental reductions, finding less of an impact on crime, while this study looked at a sudden cutback.

Crime in both New Jersey cities had decreased prior to 2008.

Researchers used monthly crime counts from 2006 to 2015 to measure the effects of Newark’s layoffs on crime and compared them with crime in Jersey City.

The authors found significant increases in overall crime, violent crime (murder, robbery, and aggravated assault), and property crime (burglary, larceny theft, and motor vehicle theft) in Newark, with overall and violent crime becoming progressively more pronounced each year. In contrast, in Jersey City, violent crime decreased steadily over the 10 years of the study, while property crime peaked in early 2009, but declined steadily afterwards.

The termination of police officers requires the remaining officers to do more with less, the authors note. In addition, letting officers go may force police to discontinue evidence-based crime prevention practices, which may impact crime levels.

The study’s authors note several limitations of their work, including that the crime data they used, which is the primary source of such information in the United States, provides an incomplete picture of crime. Also, researchers did not interview police officers or Newark officials, which the authors suggest would have added context to their findings. Lastly, while pre-layoff crime trends in Newark were not significantly different than Jersey City, it is difficult to determine whether the cities would have maintained similar crime trends if layoffs didn’t occur (which is a key assumption of evaluation research).

“As police departments determine whether to phase out specialized units to meet budgetary constraints and to enact reforms that may reduce budgets and size of police forces, our findings can inform the national debate over the impact of such actions on crime,” notes Vijay Chillar, a Ph.D. student at Rutgers University, who coauthored the study.