Irrational Exuberance

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For other uses of the term Irrational exuberance, see the Irrational exuberance (disambiguation) article.
Robert Shiller's plot of the S&P Composite Real Price Index, Earnings, Dividends, and Interest Rates, from Irrational Exuberance, 2d ed. In the preface to this edition, Shiller warns that "[t]he stock market has not come down to historical levels: the price-earnings ratio as I define it in this book is still, at this writing [2005], in the mid-20s, far higher than the historical average. … People still place too much confidence in the markets and have too strong a belief that paying attention to the gyrations in their investments will someday make them rich, and so they do not make conservative preparations for possible bad outcomes."
Robert Shiller's plot of the S&P Composite Real Price Index, Earnings, Dividends, and Interest Rates, from Irrational Exuberance, 2d ed.[1] In the preface to this edition, Shiller warns that "[t]he stock market has not come down to historical levels: the price-earnings ratio as I define it in this book is still, at this writing [2005], in the mid-20s, far higher than the historical average. … People still place too much confidence in the markets and have too strong a belief that paying attention to the gyrations in their investments will someday make them rich, and so they do not make conservative preparations for possible bad outcomes."
Price-Earnings ratios as a predictor of twenty-year returns based upon the plot by Robert Shiller (Figure 10.1, source). The horizontal axis shows the real price-earnings ratio of the S&P Composite Stock Price Index as computed in Irrational Exuberance (inflation adjusted price divided by the prior ten-year mean of inflation-adjusted earnings). The vertical axis shows the geometric average real annual return on investing in the S&P Composite Stock Price Index, reinvesting dividends, and selling twenty years later. Data from different twenty year periods is color-coded as shown in the key. See also ten-year returns. Shiller states that this plot "confirms that long-term investors—investors who commit their money to an investment for ten full years—did do well when prices were low relative to earnings at the beginning of the ten years. Long-term investors would be well advised, individually, to lower their exposure to the stock market when it is high, as it has been recently, and get into the market when it is low."
Price-Earnings ratios as a predictor of twenty-year returns based upon the plot by Robert Shiller (Figure 10.1[1], source). The horizontal axis shows the real price-earnings ratio of the S&P Composite Stock Price Index as computed in Irrational Exuberance (inflation adjusted price divided by the prior ten-year mean of inflation-adjusted earnings). The vertical axis shows the geometric average real annual return on investing in the S&P Composite Stock Price Index, reinvesting dividends, and selling twenty years later. Data from different twenty year periods is color-coded as shown in the key. See also ten-year returns. Shiller states that this plot "confirms that long-term investors—investors who commit their money to an investment for ten full years—did do well when prices were low relative to earnings at the beginning of the ten years. Long-term investors would be well advised, individually, to lower their exposure to the stock market when it is high, as it has been recently, and get into the market when it is low."[1]


Irrational Exuberance is a March 2000 book written by Yale University professor Robert Shiller, named after Alan Greenspan's "irrational exuberance" quote. Published at the height of the dot-com boom, it put forth several arguments demonstrating how the stock markets were overvalued at the time. Shiller was soon proven right when the Nasdaq peaked on the very month of the book's publication, and the stock markets collapsed right after.

The second edition of Irrational Exuberance published in 2005 is updated to cover the housing bubble, especially in the United States. Shiller writes that the real estate bubble may soon burst, and he supports his claim by showing that median home prices are now six to nine times greater than median income in some areas of the country. He also shows that home prices, when adjusted for inflation, have produced very modest returns of less than 1%/year.

Robert Shiller's plot of U.S. home prices, population, building costs, and bond yields, from Irrational Exuberance, 2d ed. Shiller shows that inflation adjusted U.S. home prices increased 0.4% per year from 1890–2004, and 0.7% per year from 1940–2004, whereas U.S. census data from 1940–2004 shows that the self-assessed value increased 2% per year.
Robert Shiller's plot of U.S. home prices, population, building costs, and bond yields, from Irrational Exuberance, 2d ed.[1] Shiller shows that inflation adjusted U.S. home prices increased 0.4% per year from 1890–2004, and 0.7% per year from 1940–2004, whereas U.S. census data from 1940–2004 shows that the self-assessed value increased 2% per year.

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