Citizenship plays no role: Someone who was bom in Ghana but has a different nationality is not understood to be an immigrant, while someone who has a Ghanaian passport but was bom abroad is understood to be an immigrant whether or not he or she already had the nationality at birth. The index represents the proportion of a group, either native- or foreign-bom, that would need to move in order to create an equal distribution. The same index can be applied to occupational distributions.