There used to be a loophole where you could change your age and gender to be an 18 year old woman, pay the lowest (pretty much token) rate, and then switch back

There used to be a loophole where you could change your age and gender to be an 18 year old woman, pay the lowest (pretty much token) rate, and then switch back to your actual age and, if necessary, gender. Now I think it looks at your history of age and gender changes, finds the combo with the highest rate, and charges that group's amount.