Rational Roots of Volatile Excess Volatility

14 Pages Posted: 7 Jul 2020 Last revised: 16 Oct 2020

See all articles by Kent Osband

Kent Osband

Institute for Studies on the Mediterranean (ISMed)

Date Written: October 16, 2020


Market prices tend to be significantly more volatile than the dividends they discount. Furthermore, volatility is not stable; it alternates between calm periods and storms of varying duration and intensity. These behaviors are often viewed as market defects or symptoms of the madness of crowds. In fact, rational learning about unstable drift provides a unified explanation. High earnings rationally breed optimism about future growth while low earnings rationally breed pessimism. This breeds excess volatility, roughly in proportion to the volatile variance of beliefs. The impact is highly significant in models fit to empirical evidence on GDP disaster risks.

Keywords: equity pricing, excess volatility, GARCH behavior, irrational exuberance, rational learning, disaster risks, doubt

JEL Classification: G12, G14, G41

Suggested Citation

Osband, Kent, Rational Roots of Volatile Excess Volatility (October 16, 2020). Available at SSRN: https://ssrn.com/abstract=3635065 or http://dx.doi.org/10.2139/ssrn.3635065

Kent Osband (Contact Author)

Institute for Studies on the Mediterranean (ISMed) ( email )


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