Text: But if the composition of the market has changed considerably, so that it is now composed largely of baby boomers investing with a 20-year--or greater--horizon, might this not change the valuation of stocks, bid up their prices, and lower the equity premium?
Entailment: If most of the market is baby boomers that could change the valuation of stocks.
Contradiction: Baby boomers do not invest in the market.