I was looking over the FAA statistics and some things come to mind. We seem to be losing pilots. There were about 358,000 private pilots in 1980, but this was down to 163,000 in 2017. A loss of 195,000. Maybe some of those moved up to commercial. In 1980 there were 183,000 commercial pilots, but this dropped to 98,000 in 2017. A loss of 85,000. I guess not. What about the totals? In 1980 there were 827,000 total pilots, but this dropped to 609,000 in 2017. A loss of 218,000. So, the question is why. It isn't the population. That's up almost 50%. It also isn't due to a shortage of instructors. In 1980 there were 60,000 instructors, which increased to 107,000 in 2017. One curious thing I found was evaporation. There were 20,000 pilots trained during WWI. Yet, by 1929 there were less than 10,000 total. Likewise, there were 400,000 pilots trained during WWII. Yet, by 1956 there were less than 258,000 total. So, apparently pilots can have a rather short active period of less than a decade. Is there a correlation with aircraft? In 1980 there were 169,000 single engine piston aircraft. These were down to 130,000 by 2016. A loss of 39,000. There were 193,000 total piston aircraft in 1980. This was down to 143,000 in 2016. A loss of 50,000. In the other hand, if we try to correlate with total aircraft there doesn't seem to be any connection. We have about the same number of total aircraft, around 220,000. There are increases in jet, turbine, rotor, experimental, and other aircraft. I suppose 'other' would pick up things like powered paraglider. I think it would include hot air balloons but I doubt that category has seen any increases. PPG however seems to be flourishing. Well, relatively speaking; PPG is actually smaller than piston multi-engine and nowhere near as big as piston singles. Still, you can see the improvements. So, I think that the high cost of a pilots license ($8,000 - $10,000) is an obstacle, however, I also think that even if we trained several hundred thousand new pilots they would just be gone again in a decade. Other than reducing the cost of flying I'm not sure what else would help.