To quantify how America is changing, we used the diversity index, which measures the chance that two people chosen at random will not be the same race and ethnicity. A high score means a county has people of many races and ethnicities, while a low score means the community is made up of a single dominant group.
To make these maps, we calculated the racial and ethnic diversity in every county in the contiguous United States for 2000, and again with the latest data from 2014.
