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Do We Really Know That Financial Markets Are Efficient?

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  • Lawrence H. Summers

Abstract

This paper examines the power of statistical tests commonly used to examine the efficiency of speculative markets. It shows that for markets with "long horizons" such as the stock markets, or the market for long term bonds, these tests have very low power. Market valuations can differ substantially and persistently from the rational expectation of the present value of cash flows without leaving statistically discernible traces in the pattern of ex-post returns. This observation also suggests that speculation is unlikely to insure rational valuations, since similar problems of identification plague both financial economists and would-be speculators.

Suggested Citation

  • Lawrence H. Summers, 1982. "Do We Really Know That Financial Markets Are Efficient?," NBER Working Papers 0994, National Bureau of Economic Research, Inc.
  • Handle: RePEc:nbr:nberwo:0994
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    1. Olivier J. Blanchard & Mark W. Watson, 1982. "Bubbles, Rational Expectations and Financial Markets," NBER Working Papers 0945, National Bureau of Economic Research, Inc.
    2. Shiller, Robert J, 1981. "Do Stock Prices Move Too Much to be Justified by Subsequent Changes in Dividends?," American Economic Review, American Economic Association, vol. 71(3), pages 421-436, June.
    3. Shiller, Robert J, 1979. "The Volatility of Long-Term Interest Rates and Expectations Models of the Term Structure," Journal of Political Economy, University of Chicago Press, vol. 87(6), pages 1190-1219, December.
    4. David S. Jones & V. Vance Roley, 1982. "Rational Expectations, the Expectations Hypothesis, and Treasury Bill Yields: An Econometric Analysis," NBER Working Papers 0869, National Bureau of Economic Research, Inc.
    5. Friedman, Benjamin M., 1979. "Optimal expectations and the extreme information assumptions of `rational expectations' macromodels," Journal of Monetary Economics, Elsevier, vol. 5(1), pages 23-41, January.
    6. Ibbotson, Roger G & Sinquefield, Rex A, 1976. "Stocks, Bonds, Bills, and Inflation: Year-by-Year Historical Returns (1926-1974)," The Journal of Business, University of Chicago Press, vol. 49(1), pages 11-47, January.
    7. Richard Meese & Kenneth S. Rogoff, 1981. "Empirical exchange rate models of the seventies: are any fit to survive?," International Finance Discussion Papers 184, Board of Governors of the Federal Reserve System (U.S.).
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    Cited by:

    1. Jeffrey A. Frankel & James H. Stock, 1983. "A Relationship Between Regression Tests and Volatility Tests of Market ncy," NBER Working Papers 1105, National Bureau of Economic Research, Inc.
    2. Mankiw, N Gregory & Romer, David & Shapiro, Matthew D, 1985. " An Unbiased Reexamination of Stock Market Volatility," Journal of Finance, American Finance Association, vol. 40(3), pages 677-687, July.
    3. Shiller, Robert J. & Huston McCulloch, J., 1990. "The term structure of interest rates," Handbook of Monetary Economics,in: B. M. Friedman & F. H. Hahn (ed.), Handbook of Monetary Economics, edition 1, volume 1, chapter 13, pages 627-722 Elsevier.
    4. Ercan Balaban & Kursat Kunter, 1996. "Financial Market Efficiency in a Developing Economy : The Turkish Case," Discussion Papers 9611, Research and Monetary Policy Department, Central Bank of the Republic of Turkey.
    5. Zapart, Christopher A., 2015. "Econophysics: A challenge to econometricians," Physica A: Statistical Mechanics and its Applications, Elsevier, vol. 419(C), pages 318-327.
    6. Ercan Balaban & Kursat Kunter, 1996. "Stock Market Efficiency in a Developing Economy : Evidence from Turkey," Discussion Papers 9612, Research and Monetary Policy Department, Central Bank of the Republic of Turkey.

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