i have no idea
but i always thought people had their pre disposed patterns and that was that, outside of any externals triggers
you lose your hair for a certain amount of time, with the same speed throughout, then it stops at whatever age. so 18 -25 bald. 18-45 semi bald, 35-45 bald. 40-80 semi bald. etc etc
all linear progressions.
never seen a case where some one goes from nw1 to nw3 in ten years, then nw3 to nw6 in two
but i guess hormones change as you get older so f*** knows
i am nw4 right now. and have been balding at a steady pace for 13/14 years. i dont expect my hairloss to just suddenly speed up soon and hit nw7 in 2 years or something. i expect to reach that norwood in another 10 going off my pattern for the last 14 years