St. Louis County is one of the most segregated places in America.
On a widely used measure of segregation, it is in the 96th percentile.
In the United States, there are 325 counties and non-incorporated cities (such as Baltimore) that have at least 20,000 people and are at least 20% black. Of them all, St. Louis County is the 12th most black-white segregated, putting it in the 96th percentile.
That figure is based on the latest available census-tract-level data from the American Community Survey, and a metric known as the "index of dissimilarity," a standard measure of segregation. (No segregation metric is perfect, of course.)
The most black-white segregated county, according to this metric, is Wayne County, Mich., home to Detroit. The least: Hertford County, N.C. (St. Louis city, which isn't part of St. Louis County, ranks 21st.)
Here’s another way of looking at it:
About 41% of black residents live in census tracts with populations that are 80% black. The national average: 21%.
In St. Louis County overall, approximately 23% of residents are black. But almost none of county's census tracts come close to that average — most have either far more black residents or far fewer. (Of the county's 199 tracts, just 28, or 14%, fall within 10 percentage points of the average.)
The most segregated areas are much poorer, too.
In census tracts where at least 80% of residents are black, 24% of the population were living below the poverty line in 2012. Just 9% of people in other tracts were.
Get the data
The full rankings of all 325 counties with at least 20,000 residents and a 20% black population:
For more information about the data and to see the computer code behind the analysis, click here.
Black–white segregation in St. Louis County ranks 12th among counties and unincorporated cities that have at least 20,000 people and are at least 20% black. An earlier version of this post indicated that the county ranked 15th. The underlying data, and rank percentile, have not changed. (h/t @MonaChalabi.)