The color of map bubbles represents the percentage point change in black population in a given city between 1910-1940 (left) and 1940-1970 (right). Darker orange shows that the black population increased as a share of the city's population. Darker blue shows that the share decreased.
However, it is important to note two key caveats in the data:
- Population shares may have changed due to migration or as a result of natural increase (births, life expectancy), though most of the change is attributable to migration.
- Data are shown only for cities "that were either in the top 100 cities in the country or top 3 of a state and had a Black population of at least 100 people." This means that some change shown on the chart may have been a shift from suburbs-to-cities or vice-versa.