Last night will be remembered as the social justice Oscars, with big winners like Patricia Arquette and Alejandro González Iñárritu using their podium time to address gender and racial inequality. But John Legend may have given the quote of the night. During his acceptance speech for Best Original Song, the singer dropped this bit of knowledge on the audience:

We know that the Voting Rights Act that they fought for 50 years ago is being compromised right now in this country today. We know that right now, the struggle for freedom and justice is real. We live in the most incarcerated country in the world. There are more black men under correctional control today than were under slavery in 1850.

At Wonkblog, my colleague Max Ehrenfreund carefully parsed this claim. It’s factual — but there are two things to keep in mind. First, people under correctional control include those on parole or probation, not just those behind bars. Furthermore, there are more than 10 times as many black people living in the United States today than in 1850. So though there may be more black people in the criminal justice system today, a far higher proportion were in slavery 165 years ago.

The American prison system is largely the domain of the states. At any given time, far more people are in state prison or local jails than in federal prison. According to the 2010 Census, only about 11 percent of people behind bars were in federal lockup. (This includes people in detention awaiting trial.)

At the federal level, only about 7 percent of convicted prisoners were guilty of a violent crime, while over half are there on drug charges. At the state level, the proportions are reversed. Just over half of people are locked up for violent crimes, while 19 percent are there for property crimes — theft, fraud, etc. — and 16 percent for drug crimes. (These numbers are from a Bureau of Justice Statistics report, which goes on to break down the populations by race.)

To put it in perspective, that is still about 46 percent of state prisoners who are behind bars for non-violent crimes. With many states struggling with overcrowding in their prisons, governors across the country are looking for ways to lower their incarceration rates, starting with the large populations of non-violent offenders.

Prison reform would make the biggest difference for black Americans. As John Legend alluded to last night, America’s incarceration system is shot through with racial disparities. Some of the worst states are in the Midwest: In places like Wisconsin, Iowa and Minnesota, black people are 10 times more likely to be in state prison or local jail.

In this chart, I used data from the Census Bureau to calculate incarceration rates for black and white Americans by state. (I excluded people in federal prison, since states have less control over that population.)

First off, it’s pretty obvious that in every state, black people are more likely to be behind bars. If incarceration rates were equal, states would fall along the diagonal line at the very bottom of this chart. But in most states, the black incarceration rate is more than four times the white incarceration rate. In nearly half of states, it’s six times the white incarceration rate.

Just look at the scale: For non-Hispanic white people, the incarceration rate ranges from 172 per 100,000 (Minnesota) to 672 (Oklahoma). For black people, the incarceration rate ranges from 845 (Hawaii) to a whopping 3,787 (Wisconsin).

The ranges for black and white people don’t even overlap. That is to say, in Hawaii, where the black incarceration rate is the lowest in the country, black people are still more likely to be locked up than white people anywhere in the United States.

Here’s another way of breaking apart the data. In places like Iowa and Minnesota, black people are more than 10 times as likely as white people to be in state prison or jail.

There’s a loose relationship between how many African Americans live in a particular state, and how large the racial disparities are in its prison population. States that have the worst gaps between the white and black incarceration rate also tend to be overwhelmingly white. These are places like Iowa, Minnesota, Vermont and Montana.

States with high black populations, particularly those in the South, have smaller disparities. In Mississippi, black people are “only” about three times as likely as white people to be in state or local lockup. Relatively speaking, the state has an unusually equitable ratio compared to the rest of America. But in absolute terms, these facts raise painful questions about the way our justice system treats people of color.