The prison population in the United States has declined modestly in recent years after three decades of growth. This is partly the result of saner sentencing policies for nonviolent drug offenders, who are more likely to be given probation and drug treatment than in the past.

At the same time, however, the number of people in prison for life has more than quadrupled since 1984 and continues to grow at a startling pace. The zealous pursuit of these sentences began in the 1970s, becoming something of a fad; it is past time to revisit the practice.

A new study from the Sentencing Project, a research group, found that one in nine inmates, about 160,000 people, is serving a life sentence. Nearly one-third of these prisoners are serving life without parole. Many of these lifers were convicted of nonviolent crimes or of crimes that occurred before they turned 18.

For much of the 20th century, a sentence as harsh as life without parole was rarely used. Instead, a person sentenced to “life” — for murder, say — could be released after 15 years when the parole board determined that he or she had been rehabilitated and no longer posed a threat. This began to change during the drug war years. Harsher sentences once reserved for people convicted of capital crimes were expanded to include robbery, assault and nonviolent drug offenses. States restricted the use of parole and governors who feared being portrayed as soft on crime began to deny virtually all clemency requests.