A major impediment to political understanding is the attitude that whatever is happening now has always been so. One of our most important tasks as political scientists is not just to describe the world as it is, but to identify and understand change.

In a recent article in the New Yorker, Kelefa Sanneh writes, “Engulfed by crime, many blacks once agitated for more police and harsher penalties,” and he quotes some African-American writers from the 1960s, who were responding to an urban crime wave.

Here’s Sanneh:

In 1962, Oberia Dempsey led a coalition of civic leaders who asked President Kennedy to “mobilize all law-enforcement agencies to unleash their collective fangs on dope pushers and smugglers.” A group convened by the civil-rights leader A. Philip Randolph urged that “a life time sentence without parole be made the punishment to meet the crime of pushing narcotics.” Testifying at a state hearing in 1969, Hulan Jack—a black state assemblyman representing Harlem, and the former Manhattan borough president—called for life imprisonment for the crime of mugging, and argued that the system of incarceration was not nearly mass enough.

But he also writes that, by the 1970s, black support for punitive anti-crime measures was disappearing:

[New York governor] Rockefeller’s drug laws sharply increased the penalties for various drug crimes; possession of four ounces of heroin, for instance, would result in a minimum sentence of fifteen years to life. . . . passed with hardly any help from black legislators, all but one of whom voted against them. When it counted most, black political support melted away.

This all makes sense to me, and it’s consistent with an analysis that Kenny Shirley and I conducted of 60 years of public opinion on the death penalty, based on an analysis of dozens of national polls where we used statistical modeling to break down opinion by state and demographics.

There’s lots of information in our recently-published paper, but here’s the quick summary.

First, the time series of support for capital punishment in the country as a whole:

Our dataset went up to 2005. What’s happening now? According to a recent Pew Research poll, capital punishment was favored by 56 percent of survey respondents and opposed by 38 percent, which gives us a proportion of support of .56/(.56+.38) = .60, that is, 60 percent support. So the death penalty remains popular but less so than in recent decades.

What about racial differences? We fit a model to track how average attitudes varied by age, sex, and state of residence. Here are our estimated time trends by race and sex:

This is not the easiest graph to read—in retrospect, I regret that we didn’t use color and that we didn’t label the lines directly—so I’ll talk you through it.

The graph shows four time series, with each flanked by lines above and below representing 95 percent uncertainty intervals. Each line shows relative support for the death penalty—that is, the national trend in the earlier graph has been subtracted so as to better display the relative positions of these four groups: white men, white women, black men, and black women. (In this analysis we lump all the non-black respondents into the “white” category, as for most of this period almost all the people surveyed would be categorized as either white or black.)

The top three lines show the estimate and uncertainty for white men, who have always been the strongest supporters of capital punishment. Below that we see white women, consistently about 10 percentage points less supportive than white men.

Below the curves get interesting: going from top to bottom, they show black men (with curves above and below for the 95 percent uncertainty interval) and black women.

At the beginning of the time series, the races did not differ so much on capital punishment. As the decades went on, though, the races have diverged, to the point in which this punishment is strongly opposed by African Americans. This steady trend is consistent with the story reported by Sanneh about the strong black support for aggressive policing in the 1960s, followed by a change in attitude during the 1970s and 1980s, continuing to the Black Lives Matter era today. Interestingly, we find the gender gap in death penalty attitudes to have declined to just about zero among African Americans, even as it remains high among whites.