With the S&P 500 up 20% this year without a single 5% pullback, how much is left in the tank?

A trader works on the floor at the New York Stock Exchange, August 27, 2021.
Source: NYSE

What more could an investor ask for? 

Stocks are having one of their best years ever in terms of gain per unit of pain, the S&P 500 up 20% not quite two-thirds of the way through 2021 without even a 5% setback along the way.

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