One of the interesting things in this mix is the size of modern aircraft. In the early 70s there was a glut of pilots as the wide bodies arrived. In longhaul a B747 could replace 2.5 B707s and the same occurred domestically when the A300 and B767s replaced the B727.
For the last 15 years or so,we have watched as the B777, A330 and 787 etc replaced the B747. I'm not including the A380 in this discussion because to a fair degree its an aberration when looking at the numbers of B747,B777 etc produced and the A380 will on work on a limited number of routes with a very limited number of airlines. This is indicated by the fact that there appears to be no second hand market for A380s at present
Avionic improvements also feature in this which has enabled flexi tracking and reduced separation standards. Both of these items were impossible to this accuracy 20 years ago.
So my point is that in the case of future pilot numbers we cant use history to indicate where this is heading and a change in one part of the equation could change everything overnight. For example a rapid rise in fuel price could make aircraft on thinner routes uneconomic and we could see say the B737s on a 10 flights/day route replaced with a wide body 3 x/ day with the obvious employment implications.
Wunwing