SPDR S&P 500 (SPY)

[spartex]

You raise some good points as it relates to retiring 68 year old baby boomers.

On the other hand the entire world population can put $$$ into S&P500 index as the keystone index for investment/retirement.

So that in and of itself is a recent growth area in the growing India and China populations entering the middle class society. I can safely guess these folks will be 4x in numbers over baby boomers leaving, though their salaries will be lower, so #'s of new workers there is what matters.

Regarding SPY dropping quickly the last minute or so of trade....
Likely the retirement index funds sell orders (reallocation) whose orders get executed in the last few minutes of trade.