[timr]

It isn't, but it's a convenient model that holds true on average.

What people actually do is say: "oh, crap...I can't make money in fixed-income securities. I guess I'll dump my retirement in stocks instead." This flood of money eventually makes its way to the riskiest stocks and props up high valuations.

[acchow]

> This flood of money eventually makes its way to the riskiest stocks

Citation needed.

[timr]

The same way it makes it to every other stock. People buy them, looking for returns.