Angela Zhou
- Assistant Professor of Data Sciences and Operations
New Research: Bail Reform Does Not Increase Crime in New York Cities
New Research: Bail Reform Does Not Increase Crime in New York Cities
Causal inference can rigorously inform executive decision-making about the actual impacts of difficult decisions on real outcomes.
New Research Shows Bail Reform Does Not Increase Crime in New York City
Requiring defendants to pay substantial amounts of cash to be released, known as money bail, has been increasingly questioned in the US. Under a money bail system, when a defendant is accused of a crime, the judge can assign a money bail amount that the defendant can pay to remain in the community, rather than detained in jail before trial.
Supporters of bail reform argue that money bail generates an unfair system where poorer defendants cannot afford their freedom, and could worsen crime by unnecessarily removing them from their communities. Opponents point to recent “increases in crime” and argue that a money bail system deters individuals from committing crimes.
Recent debates have come to the forefront of public opinion in New York's implementation of a sweeping bail reform legislation, which nearly eliminated the ability to set money bail, that took effect on January 1, 2020, was subsequently rolled back in part in July 2020, and remains contentious.
“If money bail can be eliminated without broadly increasing crime rates, then the benefits of bail reform such as restoring civil liberties, reducing racial disparities, and reducing excessive costs of pretrial detention can be enjoyed without risk to public safety in the large."
— ANGELA ZHOU, Assistant Professor of Data Sciences and Operations
The findings of a recent study by ANGELA ZHOU and an interdisciplinary team of coauthors including researchers at Cornell University and the Criminal Justice Agency, recently accepted in the Journal of Statistics and Public Policy, indicate that bail reform does not significantly increase crime overall for assault, theft, burglary and drug crimes. Though the results indicate a statistically significant increase in violent robbery, overall, there is not a statistically significant increase in crime that is caused specifically by bail reform in addition to ongoing increases in crime nationally.
“Rigorously quantifying whether bail reform is crucial to informing the debate. If money bail can be eliminated without broadly increasing crime rates, then the benefits of bail reform such as restoring civil liberties, reducing racial disparities, and reducing excessive costs of pretrial detention can be enjoyed without risk to public safety in the large,” said Zhou.
These statistically and causally quantified estimates are particularly important since recent debates have been fueled by individual anecdotes or general references to increases in crime, rather than establishing causal increases in crime because of bail reform, over and above what would have happened in the absence of bail reform. Advanced data analysis and causal inference can inform policy on timely and pressing questions of national impact.
Since New York City is a particularly urban environment, the study focuses on impacts on New York City by comparing to crime rates in large municipalities in the United States. To do so, co-author Andrew Koo merged openly available weekly data from 30 major cities to obtain the finest-grained dataset of crime rates. The study considers drug crimes, robberies, burglaries, theft, and assault.
Importantly, it is not enough to simply compare crime types before and after the reform in New York City. Though crime may be higher after the reform, this can be explained by a shared rise in crime—for example, due to national economic trends—that would have occurred anyway in the absence of bail reform. Instead of comparing crime rates in New York before and after the reform, the researchers use state-of-the-art causal methodology, the synthetic control method, to compare the before-and-after trends in crime rates of New York City to a “synthetic” New York City that emulates what would have happened to New York in the absence of the intervention. This “synthetic” New York is a certain weighted average of other large municipalities. This method lets researchers isolate the impacts of bail reform specifically on crime.
Although the analysis focuses on New York City, a growing body of evidence shows that bail reform doesn’t significantly increase crime overall. These results add to this body of evidence and have implications nationwide for pretrial policy. In fact, a recent injunction temporarily ended Los Angeles County’s use of cash bail on constitutional grounds, while in Illinois, the implementation of a recent bail reform act was blocked on legal procedural grounds.
Although the specific findings of this study are on bail reform, it exemplifies how causal inference can rigorously inform executive decision-making about the actual impacts of difficult decisions on real outcomes. This is relevant both in business and policy. It can be difficult to randomize policy or important business decisions. Despite this, advanced data analysis can handle these situations in analyzing the impacts of decisions without randomization.
“An Empirical Evaluation of the Impact of New York's Bail Reform on Crime Using Synthetic Controls”
Angela Zhou, ET AL
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