This code system http://terminology.hl7.org/CodeSystem/measure-supplemental-data-example defines the following codes:

CodeDisplayDefinition
age AgeAge Supplemental Data.
gender GenderGender Supplemental Data .
ethnicity EthnicityEthnicity Supplemental Data .
payer PayerPayer Supplemental Data.
<status value="draft"/><experimental value="false"/><publisher value="Clinical Quality Information Workgroup"/><description value="Identifier supplemental data in a population for measuring purposes."/><caseSensitive value="true"/><valueSet value="http://hl7.org/fhir/ValueSet/measure-supplemental-data-example"/><content value="complete"/><concept><code value="age"/><display value="Age"/><definition value="Age Supplemental Data."/></concept><concept><code value="gender"/><display value="Gender"/><definition value="Gender Supplemental Data ."/></concept><concept><code value="ethnicity"/><display value="Ethnicity"/><definition value="Ethnicity Supplemental Data ."/></concept><concept><code value="payer"/><display value="Payer"/><definition value="Payer Supplemental Data."/></concept></CodeSystem>