What is the rarest hair color?

How rare is red hair?

21,452 of 501,038 participants, or 4.3%, reported red natural hair at UK Biobank’s initial assessment. Red is the smallest of the five named color categories in that reference. Blonde, light brown, dark brown and black all have larger counts.

The question concerned natural adult hair color before greying. It did not ask what color someone’s hair appeared on the day of the visit. The UK Biobank field description includes the wording and separates the initial assessment from later visits.

Who is included?

This is a UK volunteer cohort recruited at ages 40–69 during 2006–2010. It is not a random sample of the world, and its participants should not be treated as a census of the UK. The 2018 UK Biobank hair-color study explains the recruitment age and shows why selecting a narrower ancestry group changes the distribution.

Our count uses the initial-assessment graph only. Adding repeat assessments would count some participants more than once. “Other”, “do not know” and “prefer not to answer” remain in the denominator, so the five named colors do not sum to 100% by themselves.

What about strawberry blonde, auburn and gray?

The published question offered broad color categories. It does not give separate counts for strawberry blonde, auburn, silver or white hair. Those descriptions cannot receive an individual frequency from this table. Someone with gray hair was asked about their color before greying; someone unsure could choose the closest natural adult color or “do not know”.

What the combined-color chart measures

The hair-and-eye chart above uses a separate study that counted both traits in the same people. Lin and colleagues, Twin Research and Human Genetics (2016), Table 2(a) reports nine combinations for 3,619 unrelated, genotyped Dutch-ancestry participants in the Netherlands Twin Register. Adults answered a 2004 survey; adolescents answered in 2005 or 2006.

Red hair with brown eyes had the smallest count: 10 participants, or 0.3% of this sample. Red with green/hazel eyes had 14 (0.4%); red with blue/gray eyes had 58 (1.6%). These are the study's broad groups. Dark hair combines light brown, dark brown and black, while red includes auburn. Blue and gray eyes cannot be separated, nor can green and hazel.

Select a pair to see its share of all participants and its share within each color group. For example, the 58 red-haired people with blue/gray eyes were 1.6% of the full sample, but 70.7% of the 82 people with red hair. The numerator is the same; the question and denominator change. The CSV includes all nine counts and all three denominators.

These are observations in a selected Dutch sample, not worldwide odds or a prediction for a child. The UK Biobank hair table and our U.S. eye-color references describe different people; multiplying their percentages would not recreate this joint measurement.