Juries around the country imposed 30 death sentences in 2016, a 40 percent drop from last year and fewer than at any time since the Supreme Court reinstated capital punishment in 1976, according to a report by the Death Penalty Information Center, a research group that opposes capital punishment. Twenty people were executed this year, the lowest number in a quarter-century.

The practice is not only increasingly rare, it is concentrated in an extremely narrow slice of the country. Only five states carried out executions in 2016, the report found, and only five imposed more than one death sentence. California sentenced nine people to die, the most of any state, but no one has been put to death there since 2006.

Public support for the death penalty keeps dropping, too — falling below 50 percent for the first time in more than four decades, according to a Pew Research survey. Support falls even further when respondents are given the alternative of a long prison term like life without parole. Though voters in California, Nebraska and Oklahoma last month preserved the death penalty, the overall trend is toward growing discomfort with state-sanctioned killing.

The total abolition of capital punishment, however, will depend on the Supreme Court’s reading of the Eighth Amendment’s ban on cruel and unusual punishments. So far, only one current member of the court, Justice Stephen Breyer, a regular critic of the death penalty, has expressed openness to examining this question. This month Justice Breyer took aim at the practice again, in a dissent from the court’s decision not to hear an appeal from a death-row inmate in Florida.