Just curious, how variant are changes in gender identification between the sexes? I probably didn't ask that right, so I'll make a claim. Just correct my percentages.
96% of transgenders born with a penis come to self-identify as female.
4% of transgenders born with a vagina come to self-identify as male.
http://www.conseil-lgbt.ca/wp-content/uploads/2013/12/How-Frequently-Does-Transsexualism-Occur.pdf
Conway finds that fewer than 1 in 5 Male-to-Female transsexuals have sex reassignment surgeries, and based on an SRS rate of 1 per 2,500 of the population, concludes that 1 in 500 people born with only male genitalia 'intensely' self identify as female; a lower bound rate of 0.2% of adult 'male' Americans. I can't find any good data on Female to Male transsexualism, but the SRS rate in that direction is considerably higher - however this may indicate that this group are more likely to have surgery, and may not say much about their general prevalence in the population.
The figures are all pretty woolly, as there is considerable social pressure for under-reporting of transsexualism; but it seems safe to say that 0.2%, or 1 in 500, is a lower bound on the prevalence of
intense transsexualism in America; and that the prevalence is in the same order of magnitude in both directions.
Assuming that figure to be correct, we would expect there to be at least six million intensely transsexual people in the US, and at least 13,000 in Tennessee (of whom at least 1,300 live in Nashville).
So at least 0.2% of people born with a penis come to self-identify as female; and a similar proportion of people born with a vagina come to self-identify as male. And many more 'feel' incorrectly gendered, but don't go so far as to publicly challenge their gender identity.
Of course, that doesn't take into account the (less common, but still numerous) people who are born with
both a penis and a vagina, or those born with
neither; Many of whom are surgically assigned a gender shortly after their birth (either of the parent's or the surgeon's choosing) and some of whom then go on to identify as the opposite gender from that assigned for them as infants.
Sexual identity is not at all the clear-cut binary situation beloved of the hard-of-thinking, even if you take the over-simplified approach of simply inspecting genitalia or chromosomes. There are people born with both genders of genitalia and with neither; there are people born with XX chromosomes and male genitalia, and with XY chromosomes and female genitalia; there are people with XXY chromosomes, and XYY chromosomes. Biology is complex, and with 7+ billion throws of the dice, there is plenty of scope for even the very rarest combinations to crop up by the thousands and tens of thousands. Transsexualism is not that rare; A conservative estimate suggests that there are at least 120 million transsexuals alive today worldwide.