America's hidden race data

• The multiracial ("Two or More Races") population grew from 9 million in 2010 to 33.8 million in 2020, per the U.S. Census.
• The multiracial population is expected to keep growing faster than most groups, and exactly how fast depends as much on how America measures race as how it lives or understands it.

Zoom in: Before the 1960s, race was often assigned by census takers. Today, it's largely self-identified.

• The U.S. Census now allows people to "mark one or more" races.
• People often change how they identify over time and across contexts, experts say. A multiracial respondent may identify as two races in one survey but as just one in another.

Friction point: The same population can produce different answers depending on how race is measured.

• Even basic analysis is difficult because the "multiracial population" isn't one group.
• Census data includes 57 different racial combinations, according to a study on Multiracial Americans by UCLA's The Civil Rights Project.
• "This raises a question of whether there is a coherent mixed-race experience such that a person who reports to be mixed-race white and Black will have the same racialized experiences as a person who reports to be mixed-race Japanese and Mexican," the authors wrote.

How it works: When multiracial Americans are miscounted or inconsistently classified, the consequences ripple across major systems.

• Studies show multiracial patients experience misidentification and racial micro-aggressions in clinical settings, which can reduce trust and engagement with care.
• Courts often treat multiracial plaintiffs as belonging to a single minority group, rather than recognizing mixed-race discrimination. That obscures how discrimination actually occurs, legal scholars say.
• Census classification rules can reassign multiracial people into single categories for redistricting and enforcement.

What they're saying: "The boundaries of race have become more fluid, and we've not fully reconciled what that means," Gregory Leslie, a political psychologist at The Ohio State University and a co-author of the UCLA report, tells Axios.

• Leslie said multiracial Americans don't fit traditional assumptions and their identities and affiliations can shift depending on environment and experience.

• "There [are] so many different ways to measure. The data is hard to get because we're measuring something dynamic with static categories."

Between the lines: A multiracial respondent, for example, with one white parent and one Asian parent, may identify as both races in one survey but as only Asian in another.

• People who identify more strongly with a political party or community are more likely to choose a single racial identity that aligns with that experience — meaning identity choices can systematically skew data.
• Two datasets measuring the same population can produce conflicting conclusions about political behavior, inequality or even population size.

Zoom out: The stakes go far beyond demographics. Mixed-race individuals often experience discrimination similar to single-race minorities, the UCLA report found.

• But outcomes vary sharply: Multiracial Americans with Black ancestry report higher rates of discrimination than other groups.
• Algorithms also trained on rigid categories may "inherit" outdated ideas of race, overriding how people identify themselves.

The bottom line: America's racial identity is evolving faster than the systems built to measure it.

• That gap risks leaving millions miscounted, misunderstood and invisible in decisions that shape their lives.