If I am 40 now and a NW 5, what will likely happen to my donor density over the next 20 years? Even though donor hair is taken from the so called "permanent" zone, does the density decrease as one ages in that zone? If the answer is yes, then some of the transplanted hair is not "permanent" but will be lost from its new location on the front of my head, just as it would have been lost from my donor area as the density decreased. Is this correct?