The S&P 500 has clinched 20 record highs this year. It also means stocks are relatively expensive.
Mandatory Credit:	Michael M. Santiago/Getty Images via CNN Newsource

The S&P 500 has clinched 20 record highs this year. It also means stocks are relatively expensive.
Mandatory Credit: Michael M. Santiago/Getty Images via CNN Newsource

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Stocks have literally never been this expensive

The S&P 500 has soared nearly 30% since its low point in April and investors have cheered the index’s ascent to record highs. The market’s rally also means stocks are relatively expensive — and more vulnerable to a surprise.