Mandatory minimum sentences deter crime

The claim

Proponents of mandatory minimum sentencing argue that long, predetermined prison terms serve two complementary functions: deterrence and incapacitation. The deterrence argument holds that when potential offenders know in advance the exact penalty attached to a crime — and that a judge cannot reduce it — they perform a rational cost-benefit calculation and choose not to offend. The incapacitation argument holds that even if deterrence is incomplete, offenders confined for ten or twenty years cannot commit crimes in the community during that time, producing a mechanical crime-reduction effect. Taken together, these claims have underwritten decades of US sentencing policy, from the Rockefeller Drug Laws of 1973 to the federal Anti-Drug Abuse Act of 1986 and the wave of state “three strikes” statutes in the 1990s.

The mechanism

The deterrence mechanism rests on classical rational-choice theory: an actor weighs the expected cost (probability × severity of punishment) against the expected benefit of an offense. If that calculation holds, then increasing either the probability of punishment or its severity should reduce crime. The incapacitation mechanism is more mechanical and makes no assumption about rationality — a person in prison cannot commit street crime.

Both mechanisms have surface plausibility, but they diverge sharply in the empirical literature. The deterrence channel depends critically on which variable is manipulated. Certainty of punishment — the probability that an offense is detected and punished at all — has robust empirical support as a deterrent. Severity of punishment, conditional on being caught, has much weaker support and in most well-controlled studies has no statistically significant effect on crime rates. The policy implication is consequential: mandatory minimums increase severity without changing certainty (arrest rates are set by policing, not sentencing), and the theory therefore predicts they should have little deterrent effect — which is precisely what the evidence shows.

The incapacitation mechanism is real but subject to sharp diminishing returns. The first years of incarceration remove high-rate offenders from circulation; extended sentences increasingly incapacitate individuals who would have aged out of crime naturally. After roughly age 35, criminal offending drops steeply for most offense categories, meaning long mandatory terms impose large costs to incapacitate people during their least criminally active years.

The evidence

The National Academy of Sciences 2014 meta-review

The most authoritative synthesis of the deterrence literature is the 2014 National Academy of Sciences report, The Growth of Incarceration in the United States, edited by Travis, Western, and Redburn. The panel reviewed decades of quasi-experimental studies and concluded that increases in sentence length have not been shown to reduce crime rates. The report explicitly distinguished this finding from the certainty literature, which does support deterrence effects. The NAS panel found that the US incarceration rate — which grew from roughly 100 per 100,000 in 1970 to 756 per 100,000 at its 2008 peak — produced diminishing crime-control returns over the period and that continued increases in incarceration would have “a small or null effect on crime rates.”

Durlauf and Nagin on certainty versus severity

Economists Steven Durlauf and Daniel Nagin conducted a formal review and re-analysis of the deterrence literature, published in Criminology and Public Policy (2011). They concluded that the elasticity of crime with respect to certainty of punishment is substantially larger than the elasticity with respect to severity. Their analysis found that reallocating resources from imprisonment to policing — which increases certainty — would reduce crime more cost-effectively than extending sentence lengths. This finding has been independently replicated by Chalfin and McCrary (2018), who estimated that a one percent increase in police size reduces violent crime by roughly 0.3 to 0.5 percent, while marginal increases in incarceration produce effects an order of magnitude smaller per dollar spent.

Drug mandatory minimums and drug use rates

The 1986 Anti-Drug Abuse Act introduced the 5-year mandatory minimum for possession of 5 grams of crack cocaine, among other provisions. If severity-based deterrence functioned as claimed, drug use rates should have declined in the years following enactment. National Survey on Drug Use and Health data, and predecessor surveys, show no such decline. Drug use rates fluctuated with demographic and cultural trends largely independent of sentencing policy. Meanwhile, drug arrest rates rose sharply, drug incarceration increased by roughly 1,100 percent between 1980 and 2010, and the US spends approximately $50 billion annually on drug enforcement — without evidence that mandatory minimums drove the reductions in drug use that did eventually occur in specific substances.

Cross-national comparisons

Germany operates under a sentencing framework that explicitly limits the use of prison for sentences under six months, emphasizes proportionality, and invests heavily in rehabilitation. German maximum sentences for equivalent drug offenses are a fraction of US mandatory minimums. Germany’s homicide rate is approximately 0.8 per 100,000; the US rate is approximately 6.8. The Netherlands incarceration rate is 62 per 100,000 — roughly one-tenth the US peak — and Dutch crime rates for most offense categories are comparable to or lower than the US. Norway’s Halden Prison is the global reference point for rehabilitative incarceration: the facility provides education, vocational training, and psychological services, with Norway’s 2-year recidivism rate approximately 20 percent against the US rate above 44 percent within the same window. These cross-national contrasts do not by themselves establish causation, but they are inconsistent with the claim that long mandatory terms are necessary to achieve public safety.

State-level rollbacks as natural experiments

New York repealed most of its Rockefeller Drug Laws between 2004 and 2009. Connecticut, California, and South Carolina have each reduced mandatory minimums for various offense categories in the past two decades. Systematic reviews of these policy changes have not found corresponding increases in crime rates. The Brennan Center for Justice (2021) analyzed state-level sentencing reforms and found that states reducing incarceration experienced equivalent or greater crime declines than states maintaining high incarceration levels during the same period.

Prosecutorial discretion and racial disparity

A structural consequence of mandatory minimums that is rarely acknowledged in deterrence arguments is that they shift sentencing discretion from judges to prosecutors. Charging decisions — which determine whether a mandatory minimum is triggered — are less transparent than judicial sentencing and subject to documented racial disparities. The US Sentencing Commission (2017) found that Black male defendants in federal drug cases received sentences on average 13.1 percent longer than similarly situated white male defendants, largely attributable to prosecutorial charging of mandatory-minimum-triggering offenses at different rates. This disparity undermines the rational-actor premise of deterrence theory: if the punishment faced is not uniform across defendants for identical conduct, the mechanism cannot function as described.

Who benefits

The mandatory minimum regime produces identifiable institutional beneficiaries. The private prison industry — GEO Group and CoreCivic collectively earned over $4 billion in revenue in 2019 — depends directly on high incarceration rates and has lobbied through the American Legislative Exchange Council (ALEC) for three-strikes and truth-in-sentencing legislation. Federal prosecutors have used mandatory minimum charging as leverage to extract plea agreements, which now account for approximately 97 percent of federal convictions; this concentration of power serves prosecutorial career incentives and office conviction-rate metrics. Politicians across both parties have used mandatory minimum legislation as a low-cost signal of toughness on crime to constituencies, particularly in election cycles following high-profile violent crimes. Rural counties that host prisons benefit economically from incarceration employment, creating a constituency for high imprisonment that is geographically and politically distinct from the communities most affected by aggressive sentencing.

The counter

The incapacitation claim has genuine empirical grounding at the margins. Studies using natural experiments — such as Owens (2009) on juvenile justice and Barbarino and Mastrobuoni (2014) on Italian prisoner amnesties — do find that releasing high-rate offenders increases local crime. The first-order incapacitation effect is real. Critics of mandatory minimum reform are therefore not without any empirical basis when they argue that some offenders require long-term confinement for public safety reasons, particularly in violent offense categories.

The deterrence literature is also not uniformly negative. Helland and Tabarrok (2007) found evidence of a deterrent effect from California’s three-strikes law on individuals with two prior strikes, consistent with certainty effects when the relevant population knew precisely that a third conviction would trigger life imprisonment. This suggests that highly salient, near-certain sentencing enhancements directed at high-risk populations may have deterrent value — a more targeted claim than the general mandatory minimum regime provides.

What the evidence does not support is the broad application of mandatory minimums across low-level drug offenses, the claim that sentence length is the operative deterrent variable, or the assertion that the scale of US incarceration has produced safety gains proportional to its costs. The strongest version of the structural critique is not that punishment has no deterrent effect, but that mandatory minimums are among the least efficient instruments for achieving it.

References

Travis, J., Western, B., & Redburn, S. (Eds.). (2014). The growth of incarceration in the United States: Exploring causes and consequences. National Academies Press. https://doi.org/10.17226/18613

Durlauf, S. N., & Nagin, D. S. (2011). Imprisonment and crime: Can both be reduced? Criminology and Public Policy, 10(1), 13–54. https://doi.org/10.1111/j.1745-9133.2010.00680.x

Chalfin, A., & McCrary, J. (2018). Are U.S. cities underpoliced? Theory and evidence. Review of Economics and Statistics, 100(1), 167–186. https://doi.org/10.1162/REST_a_00694

Owens, E. G. (2009). More time, less crime? Estimating the incapacitative effect of sentence enhancements. Journal of Law and Economics, 52(3), 551–579. https://doi.org/10.1086/598510

Helland, E., & Tabarrok, A. (2007). Does three strikes deter? A nonparametric estimation. Journal of Human Resources, 42(2), 309–330. https://doi.org/10.3368/jhr.XLII.2.309

Barbarino, A., & Mastrobuoni, G. (2014). The incapacitation effect of incarceration: Evidence from several Italian collective pardons. American Economic Journal: Economic Policy, 6(1), 1–37. https://doi.org/10.1257/pol.6.1.1

US Sentencing Commission. (2017). Demographic differences in federal sentencing: A focus on early identification of disparities. United States Sentencing Commission.

Brennan Center for Justice. (2021). The myth of prison as crime deterrent. New York University School of Law.

Beckett, K., & Sasson, T. (2004). The politics of injustice: Crime and punishment in America (2nd ed.). Sage Publications.

Sentencing Project. (2023). State of criminal justice 2023. The Sentencing Project. https://www.sentencingproject.org/reports/the-state-of-criminal-justice-2023/