Racial disparities of many kinds rightly inspire concern these days. One of the most distressing gaps — if not one of the most frequently discussed — was described in a May 20 presentation before the Minneapolis City Council's Public Safety Committee.

Coming a few days before a particularly violent weekend, and in the wake of the shootings of three young Minneapolis children, the Police Department report detailed the city's 2021 crime surge up to that point.

There had been 187 shootings in Minneapolis since Jan. 1 — two-and-a-half times the pace of gunplay in the same period a year earlier.

And 87% of the victims were Black.

No details on the shooters were presented. But federal Department of Justice data released last September indicated that, nationwide, about 70% of Black victims of violent crime are victimized by Black assailants.

With Black residents making up about 20% of the Minneapolis population, it's startling that while the new crime wave is a disaster for the entire community, its heaviest burdens are falling so disproportionately among African Americans.

It would seem that nothing could be more critical amid today's almost universal pledges to strive toward a more racially just America than to think carefully and seriously about the current freewheeling debate over policing, crime and how to slow the bloodshed.

One theory being forcefully offered holds that what's needed is less policing, at least in the traditional sense; the better to focus on the root causes of violence and avoid the harms of heavy-handed law enforcement. Another view argues that more police presence is urgently required, albeit from better trained and disciplined officers.

Now comes impressive new research — brought to my attention by the Washington Post's excellent Megan McArdle — into precisely the basic questions at hand.

1) Do more cops on city streets reduce crime — and if so, for whom?

2) Do more cops inflict more harassment, more incarceration and more use of force — and if so, against whom?

In short, is policing all about "preserving white comfort at the expense of others," as former Minneapolis Mayor Betsy Hodges put it last summer in a New York Times piece reprinted on these pages? Do "police ... politely stand guard in predominantly white parts of town ... [while they] aggressively patrol the parts of town where people of color live ..."?

Less dramatically, researchers Aaron Chalfin (University of Pennsylvania), Emily Weisburst (UCLA), Benjamin Hansen (University of Oregon) and Morgan Williams (NYU) frame the key issue this way: "The extent to which the benefits of additional law enforcement accrue equally to Black and white Americans remains a surprisingly open question."

These scholars, unlike so many others in this dispute, take the surprisingly rare step of seeking facts to provide an answer. They find some clarity but also sobering policy trade-offs — often the fingerprints of reality — rather than the kind of pain-free solutions imagined by ideologues of every stripe.

The study looked at changes in police force size, crime and arrests in 242 large American cities over nearly 40 years. Fundamentally, it found that "investments in law enforcement save Black lives," (that is, especially Black lives) but at the cost of more low-level "quality of life" arrests and all the insults and injuries of intensive policing, again especially among Black residents.

The scholars note an irony in that "American support for law enforcement is at its lowest point" in decades — "despite the dramatic decline in crime since the 1990s."

But the irony may actually explain itself. "[A]bated homicides are ... difficult ... to observe," the report notes, compared with arrests, traffic stops and other encounters with cops.

Nobody, in short, sees the crimes that vigorous policing prevents — while they can't miss the hardships and occasional tragedies it brings, especially in high crime, minority neighborhoods.

But while acknowledging that other, non-police approaches to public safety are worth exploring and expanding, " 'de-funding' the police could result in more homicides, especially among Black victims," these researchers say.

Their calculations reveal that, on average, one homicide is prevented per year for every 10 to 17 additional police officers employed, depending on the city. Murders decline "in total and for each racial group." But adjusted for population "the decline is twice as large for Black victims."

Meanwhile, with more cops on the street arrests increase for low-level offenses — "in particular for Black civilians and especially ... in cities with a large Black population."

Yet in what may be the least expected outcome, the researchers find that more police presence leads to a drop in overall arrests for the full-range of serious violent crimes, again "disproportionately for Black civilians."

The result of an apparent deterrent effect from more visible policing, the report calls this "a 'double dividend' for society" — "reductions in both crime and incarcerations for serious offenses."

All this said, the study cautions that the beneficial effects of larger police forces seem much smaller, even nonexistent, in cities with the largest Black populations. (Minneapolis' Black population is just below average for the cities studied.) More police-civilian encounters, meantime, carry risks, and increased low-level arrests can produce criminal records that burden lives.

The scholars say their findings "are consistent with the idea that Black communities are simultaneously over- and under-policed."

A better balance has to be the goal. But it's hard to believe we've found it in these tragic recent months.

D.J. Tice is at Doug.Tice@startribune.com.