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

CodeDisplayDefinition
age AgeAge Stratification.
gender GenderGender Stratification.
region RegionRegion Stratification.
<status value="draft"/><experimental value="false"/><publisher value="Clinical Quality Information Workgroup"/><description value="Identifier subgroups in a population for measuring purposes."/><caseSensitive value="true"/><valueSet value="http://hl7.org/fhir/ValueSet/measure-stratifier-example"/><content value="complete"/><concept><code value="age"/><display value="Age"/><definition value="Age Stratification."/></concept><concept><code value="gender"/><display value="Gender"/><definition value="Gender Stratification."/></concept><concept><code value="region"/><display value="Region"/><definition value="Region Stratification."/></concept></CodeSystem>