Lubos Pastor and Robert Stambaugh argue that long-horizon stock investors actually face more volatility than short-horizon investors. How should investors interpret this evidence? KRF: The Pastor-Stambaugh result is driven by uncertainty about the true expected return. The volatility or standard deviation of returns is usually defined as the expected variation relative to the true mean of the process generating returns - as if we knew the true expected return. But, as Pastor and Stambaugh emphasize, we never actually know the true mean. When they include uncertainty about the true mean (as well as uncertainty about other true parameters) in the analysis, they find that long-run returns are indeed more volatile than short-run returns. (Read the full entry)
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