There is no exact number of transsexuals in the world, but it is estimated to be over 174,140,740 people.
Blanchard's transsexualism typology (also Blanchard autogynephilia theory (BAT) and Blanchard's taxonomy) is a psychological typology of male-to-female (MtF) transsexualism created by Ray Blanchard through the 1980s and 1990s, building on the work of his colleague, Kurt Freund. Blanchard divided trans women into two different groups: so-called "homosexual transsexuals," whom Blanchard says seek sex reassignment surgery to romantically and sexually attract (ideally heterosexual) men, and "autogynephilic transsexuals" who purportedly are sexually aroused at the idea of having a normative female body. The typology suggests distinctions between MtF transsexuals, but does not speculate on the causes of transsexualism. The distinction is a recurring theme in scholarly literature on transsexualism.
Supporters of the theory include J. Michael Bailey, Anne Lawrence, James Cantor, and others who say that there are significant differences between the two proposed groups, including sexuality, age of transition, ethnicity, IQ, fetishism, and quality of adjustment. Criticism of the research and theory has come from John Bancroft, Jaimie Veale, Larry Nuttbrock, Charles Allen Moser, Julia Serano, and others who say that the theory is poorly representative of trans women, reduces gender identity to a matter of attraction, is non-instructive, that the research cited in support of the theory has inadequate control groups or is contradicted by other data, and that its proponents routinely make statements that call into question the theory's falsifiability.