I only identify with my birth gender by default: 681, 45.3%

I'm surprised at this. Is there a special term for "only identifying with one's gender by default" or keywords I can use to look for statistics for among the general population? (a brief googling didn't uncover anything). I would've guessed this number to be much lower, and now I'm wondering whether this is signaling or whether my model of other people in this particular instance is completely wrong.