PLoS ONE (Jan 2020)

Fear and stock price bubbles.

  • Thorsten Lehnert

DOI
https://doi.org/10.1371/journal.pone.0233024
Journal volume & issue
Vol. 15, no. 5
p. e0233024

Abstract

Read online

I evaluate Alan Greenspan's claim that stock price bubbles build up in periods of euphoria and tend to burst due to increasing fear. Indeed, there is evidence that e.g. during a crisis, triggered by increasing fear, both qualitative and quantitative measures of risk aversion increase substantially. It is argued that fear is a potential mechanism underlying financial decisions and drives the countercyclical risk aversion. Inspired by this evidence, I construct an euphoria/fear index, which is based on an economic model of time varying risk aversion. Based on US industry returns 1959-2014, my findings suggest that (1) Greenspan is correct in that the price run-up initially occurs in periods of euphoria followed by a crash due to increasing fear; (2) on average already roughly a year before an industry is crashing, euphoria is turning into fear, while the market is still bullish; (3) there is no particular euphoria-fear-pattern for price-runs in industries that do not subsequently crash. I interpret the evidence in favor of Greenspan, who was labeled "Mr. Bubble" by the New York Times, and who was accused to be a serial bubble blower.