Let this be your final warning on U.S. stocks' overvaluation

``As stock prices soar to new heights, the S&P 500 Index has now reached levels of overvaluation only ever seen during the dot-com bubble and in 1929 -- an eye-watering 31 on the measure known as the "Shiller PE" ratio. But even if we fudge the numbers and exclude the depressed earnings from the global financial crisis a decade ago, we still get a reading of 25.5. That's still way up there, and in almost 150 years, every time stocks have gotten anywhere close, they've come crashing down again.''