A comprehensive new report from the National Research Council (NRC) examining mass incarceration in the United States has concluded that lengthy prison sentences are not the most effective means of deterring crime. Over a span of four decades, from 1972 to 2012, the U.S. incarceration rate quadrupled, largely due to the implementation of harsher sentencing policies, particularly for drug-related offenses. This alarming trend was documented in the report, which was commissioned by the U.S. Department of Justice and synthesizes extensive research on the topic.
The report draws heavily from past studies to argue that increasing the severity of criminal penalties does little to deter individuals from committing crimes. For instance, an analysis of a federal program in Virginia that imposed enhanced punishments for gun-related offenses found no evidence that the threat of longer sentences had any meaningful deterrent effect. Similarly, studies examining adolescent behavior revealed that teenagers did not significantly reduce their criminal activity after turning 18, despite facing more severe legal consequences as adults. One study noted a small decline in crime rates among this demographic, but the reduction was minimal and statistically insignificant.
Another notable example cited in the report is California’s “three-strikes” law, which mandates a minimum sentence of 25 years to life for individuals convicted of a third felony offense. While some studies suggested the law may have had a modest deterrent effect—reducing the felony crime rate by up to 2% among individuals with two prior strikes—the impact was negligible overall. Moreover, even when such laws were found to deter crime to some extent, the costs associated with incarcerating individuals for extended periods often outweighed any potential benefits. As the report notes, “Evidence is limited on the crime prevention effects of most of the policies that contributed to the post-1973 increase in incarceration rates. Nevertheless, the evidence base demonstrates that lengthy prison sentences are ineffective as a crime control measure.”
Rather than focusing on the length of prison terms, the report emphasizes that the certainty and immediacy of punishment play a far greater role in deterring criminal behavior. To illustrate this point, the authors highlight a program implemented in Hawaii known as HOPE (Hawaii’s Opportunity Probation with Enforcement). Under this initiative, probationers who failed drug tests faced swift but brief sanctions, typically one or two days of confinement. Compared to those who did not face such immediate consequences, offenders in the HOPE program showed dramatically fewer positive drug tests, demonstrating that prompt accountability can be a powerful motivator for compliance.
Based on these findings, the report makes several recommendations aimed at reducing the nation’s reliance on mass incarceration while maintaining public safety. It urges federal and state policymakers to reconsider mandatory minimum sentencing laws and other policies that contribute to excessively long prison terms. These measures, the report argues, have yielded only marginal reductions in crime while imposing significant financial, social, and human costs. Instead, the report advocates for a shift toward evidence-based approaches that prioritize rehabilitation, community supervision, and alternative forms of punishment tailored to individual circumstances.
In addition, the report calls for further research into the complex relationship between sentence lengths and deterrence. While existing data suggests that shorter sentences coupled with swift and certain enforcement may achieve better outcomes, gaps remain in our understanding of how different factors influence criminal behavior. By investing in rigorous scientific inquiry, lawmakers can develop more nuanced and effective strategies for addressing crime without perpetuating the harms caused by over-incarceration.
Ultimately, the NRC report underscores the need for a fundamental reevaluation of America’s approach to criminal justice. With nearly 2 million people currently incarcerated across the country—a figure that far exceeds that of any other developed nation—the economic burden and societal toll of mass imprisonment are unsustainable. The report concludes that reducing incarceration rates through smarter, more equitable policies will not only promote fairness within the justice system but also enhance public safety by freeing resources to address the root causes of crime.