Size and Distribution of Transgender and Gender Nonconforming Populations: A Narrative Review.

Accurate estimates of the number and proportion of transgender and gender nonconforming people in a population are necessary for developing data-based policy and for planning and funding of health care delivery and research. The wide range of estimates reported in the literature is attributable primarily to differences in definitions. Other sources of variability include diverse cultural and geographic settings and important secular trends. The transgender and gender nonconforming population is undergoing rapid changes in size and demographic characteristics. More accurate and precise estimates will be available when population censuses collect data on sex assigned at birth and gender identity.