Are US stock market highs justified, or is there a bubble? | Robert Shiller

Massive earnings might reflect strength - but history suggests we should expect volatility

The US stock market, as measured by the monthly real (inflation-adjusted) S&P Composite Index, or S&P 500, has increased 3.3-fold since its bottom in March 2009. This makes the US stock market the most expensive in the world, according to the cyclically adjusted price-to-earnings (CAPE) ratio that I have long advocated. Is the price increase justified, or are we witnessing a bubble?

One might think the increase is justified, given that real quarterly S&P 500 reported earnings per share rose 3.8-fold over essentially the same period, from the first quarter of 2009 to the second quarter of 2018. In fact, the price increase was a little less than equal to earnings.

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