History repeats itself.<p><a href="https://en.wikipedia.org/wiki/Institut_f%C3%BCr_Sexualwissenschaft#Nazi_era" rel="nofollow">https://en.wikipedia.org/wiki/Institut_f%C3%BCr_Sexualwissen...</a>
The important variable to record is sex.<p>If researchers want to record "gender identity" or similar ideologically-driven claims then this should have to be justified. And probably labelled as something more to the point, e.g. "does this individual have a strong desire to be the opposite sex?"