Assumptions:
* index funds are larger and larger share of investing
* Median Baby boomer about 63
* 1/2 Americans in stock market
* In 2017, over 62 million Americans receive SS benefits
* US Adult Population 247,773,709 = 123M in stock market
* Only 25 M generation X
* Millennials don't invest in stocks http://www.businessinsider.com/why-so-few-millennials-invest...
Conclusion Drain of stock market as sellers begin to out number buyers