The Census Bureau’s measure of diversity is based on the probability that two randomly chosen people in a given place belong to different racial and ethnic groups. In a location where one racial group is 100% of the population that probability is 0%. That probability jumps to 50% where two groups make up exactly half of the population. The higher the probability, the higher the diversity for that location.
2020’s least diverse county was Starr County on the Texas-Mexico border. With a population that was 98% Hispanic, there’s less than a one in 20 chance that two random people in the county come from one of eight different racial or ethnic groups.
Every state and Washington, DC became more diverse between 2010 and 2020. The non-Hispanic white population share dropped in every state, but increased in Washington, DC. The Hispanic population share grew in every state. The Asian population grew in all but one state, Hawaii, where it remains the largest demographic group.
In fact, Hawaii is the nation’s most diverse state, with multiracial, Asian, and white groups each representing more than 20% of the population. Maine, the only state where the non-Hispanic white share is more than 90% of the population, is the least diverse state.
While North Dakota is the fifth-lowest state for diversity, it also grew the most in diversity between censuses. Non-Hispanic white people dropped from 89% to 83%, while its Hispanic, Asian, Black, and multiracial populations all grew.
What diversity (or lack of diversity) looks like locally
Thirty-seven percent of Americans, or about 124 million people, live in counties that are more diverse than the US overall. This includes 36 out of the 49 counties with a population of more than a million people. Queens County in New York — home to more than 2.4 million people — is the most diverse of those large counties. There, no racial or ethnic group is more than 28% of the population. There are five counties more diverse than Queens and all are in Alaska or Hawaii.
Fewer than 2 million people live in counties where there is less than a 10% likelihood of meeting two random people of different demographics. Non-Hispanic white people are more than 95% of the population in all but four of these counties. Most are in the Midwest or Great Plains, though three are majority Hispanic counties along the Texas border. Another is a majority native area in Alaska.
Fifteen percent of Americans, or 45.5 million people, live in counties where diversity increased by 10%. These counties are in 44 states and vary in size. This includes three counties home to more than 1 million people: King County in Washington, Middlesex County in Massachusetts, and Collin County in Texas. The biggest change in diversity came in Williams County, North Dakota. Its population grew from 23,000 in 2010 to 41,000 in 2020, while the share of its non-Hispanic white population dropped from 91% to 76%.
Five percent or 17 million Americans live in counties that are less diverse than they were in 2010. These counties include five with populations exceeding 1 million — Florida’s Miami-Dade County; San Bernardino, Santa Clara, and Fresno in California; and Bronx County in New York. Hispanic Americans were already the largest demographic group in those counties except for Santa Clara, and contributed most to those four counties’ growth. In Santa Clara, most of its population growth was attributed to Asian Americans, the county’s largest demographic group.
Examining racial and ethnic makeup is just one way to use census data to understand the changing country. For more on demographics, visit the Demographics and Population page.