The murder rate has fallen by two thirds since 2018, and crime has fallen by 75%, in El Salvador as it has imprisoned large numbers of criminals. The country has put nearly 2% of its adult population in prison. This is due to the anti-crime policies of its current president, Nayib Bukele. …

Harsher penalties discourage crime. Crime in California fell significantly after California voters adopted Proposition 8, which mandated longer sentences for repeat offenders who kill, rape, and rob others. A study found those longer sentences deterred many crimes from being committed. Similarly, a 2008 Santa Clara University study found that longer sentences for three-time offenders led to “significantly faster rates of decline in robbery, burglary, larceny, and motor vehicle theft.”

In addition to deterring crimes by people outside of prison, longer sentences also keep dangerous people locked up so they can’t harm law-abiding people. Killings have increased in Baltimore, where most killings are committed by people who previously were convicted of a serious crime, but who are no longer in jail due to their past lenient sentence.

Shorter sentences also make inmates more likely to reoffend and commit more crimes.