Law enforcement and academics agree that three factors are involved in deterring crime: certainty of apprehension, swiftness of apprehension, and severity of sanctions—in other words, how likely you are to get caught, how quickly you get caught, and how long you spend in prison if you get caught. The two groups disagree, however, about which of these is most important for deterrence. Modern academics insist that length of prison sentences is not crucial, while law enforcement officials believe that the length of incarceration time actually stops people from committing crimes in the future. In a recent report, the United States Sentencing Commission put this question through a rigorous statistical testing procedure involving thousands of inmates over multiple decades and came up with a clear result: length of incarceration matters for recidivism—a lot.

Academics take a negative view of stiff sentences. Some argue that longer sentences have no effect on recidivism. Other scholars argue that longer sentences are criminogenic—that is, they cause people to be more likely to commit crimes when they are released. Liberal advocacy groups claim that shorter sentences would actually reduce future offending. But a thorough review of the literature by separate groups of respected scholars in 2009 and 2022 concluded that much of the academic research regarding the effect of length of incarceration on recidivism suffered from serious methodological flaws, including too-small study sizes and ill-advised attempts to judge the impact of minor differences in incarceration.

The United States Sentencing Commission, using its access to massive amounts of data about thousands of federal criminal defendants over many decades, decided to test the effects of incarceration on recidivism. The commission chose to study 32,135 federal criminal defendants released in 2010. The study divided the defendants into five groups based on length of sentence: 24–36 months, 36–48 months, 48–60 months, 60–120 months, and more than 120 months. The commission then checked to see which of the released defendants committed new crimes during an eight-year follow-up period.

The results were compelling. For defendants receiving a sentence of more than 60 months (five years), the odds of recidivism were 18 percent lower than a matched group of prisoners receiving shorter sentences. For defendants with sentences of more than 120 months (ten years), the odds of recidivism were 29 percent lower. These conclusions were statistically significant at p<0.001—a statistical measure that shows profound reliability. No statistically significant difference in recidivism was found for defendants serving less than 60 months.

Contrary to current academic thinking, then, the length of a criminal’s sentence matters quite a bit in reducing future offending. Why are these findings so important? First, because they offer a stern rebuttal to the academic literature downplaying the effect of lengthy sentences; the commission even devotes an entire section of its report to assessing these studies. But perhaps more importantly, the commission’s findings are a blow to progressive prosecutors, who have been relying on flawed academic literature to push for lower sentences for just about every crime, even violent ones, claiming that reduced sentences will not cause more crime. One of the main proponents of this philosophy is Philadelphia district attorney Larry Krasner, who specifically criticized sentences longer than five years, promised that crime would drop if he avoided lengthy sentences, and scoffed at law enforcement officials who warned him of the consequences if he enacted his policies. Krasner delivered on his promises, dropping murder charges even in the case of video evidence and handing out lenient sentences. The predictable result: violent criminals have overrun Philadelphia, with murder soaring to an all-time record and police officers shot during a Fourth of July celebration.

This isn’t the first time that the Sentencing Commission has looked at the link between sentence length and recidivism. In a prior study of inmates released in 2005, the commission found substantively similar results. It redid the study in 2022 with inmates released in 2010 to address criticisms by public defenders of the first study. In the world of statistics, this is known as the replication of a study. Consistent results with new data suggest strongly that both studies are valid.

To summarize: lengthy prison sentences play an important role in stopping criminals from reoffending. When experts talk about deterrence being built on certainty, swiftness, and severity of sanctions, they need to recognize that all three factors work together to stop crime. As even the commission’s study found, relatively light sentences of less than 60 months don’t do much to stop defendants from committing crimes again, while longer sentences have a much better chance of success.

One final aspect of this study bears mentioning: the commission’s report linking longer sentences to less crime came out under the Biden administration. Like Bill Clinton in the 1990s, even Joe Biden’s own experts are telling him that longer sentences help curtail crime. Clinton listened, enacting tough-on-crime legislation in conjunction with a Republican-controlled Congress—and crime declined for decades. Now violent crime is surging again. Will Biden follow the data?

Photo: MoreISO/iStock


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