I’m not sure if there is a surefire metric that can be used for this kind of exposure, but violent crimes are probably decent proxies. For example, according to the most recent US demographic breakdown, and FBI crime statistics [0], black Americans are about 4x more likely to commit murder than white Americans. So if that were to be used as a measure of exposure to potential police violence, they might actually be less likely to be killed by police than a white person, given the number of situations in which police violence has potential to occur.
It’s important to note that this doesn’t mean black Americans aren’t the victims of systemic racism. But it means that the racism is occurring not necessarily due to trigger happy cops who hate black people, but due to a society in which black people are disenfranchised in more banal, but impactful, ways (educationally, economically, socially), which results in higher crime rates, which results in more police contact/confrontation, which results in more deaths at the hands of the police.
This is all to say that many of the “defund the police” efforts, while understandable as a knee jerk reaction to police violence we sometimes see, is fundamentally misguided. It’s akin to campaigning against chemotherapy, because lots of chemotherapy recipients end up dying. Defunding the police won’t change the underlying systemic racism that is the source of the problem, and if anything will exacerbate it. This is reflected in polling of black Americans who live this reality, the majority of whom want more policing in their communities.
[0] https://ucr.fbi.gov/crime-in-the-u.s/2019/crime-in-the-u.s.-...