<p>Possible values for ethnic background in the UKB (Data-Field 21000).</p>

Participants are first asked “What is your ethnic group?” and then asked “What is your ethnic background?” For “Chinese”, there is no second question. Participants may also select “Prefer not to answer” for the second question; it is possible to have ethnic background recorded as ethnic group (e.g. just “White” or “Mixed”). Excluding “Do not know”, “Prefer not to answer”, and “Not available”, there were 20 unique values of ethnic background.
(XLSX)