Compared with 1980, more census tracts today are in the middle of this distribution, with a mix of white residents and other groups. But the center here has grown primarily because the right side has collapsed.

In 1980, about a quarter of the census tracts in America were almost exclusively white — 97 percent non-Hispanic white or more — and one-third of white residents lived in such a neighborhood. Those figures are probably undercounts, as the 1980 census lacked tract boundaries for much of rural America. But by the latest census data, just 5 percent of white residents live in such a place, mostly in rural areas.

These charts informed how we thought about neighborhood racial change in a project The Upshot published over the weekend. Most neighborhoods in America that have become more diverse have shifted from the right side of that picture toward the center; Hispanics, Asian-Americans and African-Americans have moved into once predominantly white communities.

Places in Gwinnett County, Ga., that were more rural and almost all white in 1980, for example, have grown in population to become diverse suburbs of Atlanta today. Affluent sections of Bergen County, N.J., have become more diverse with the arrival of Asian immigrants. The white working-class Milwaukee suburb of West Allis has seen an inflow of Hispanic residents.