Why Has Idiosyncratic Risk Been Historically Low in Recent Years?

45 Pages Posted: 24 Jan 2018

See all articles by Söhnke M. Bartram

Söhnke M. Bartram

Warwick Business School - Department of Finance

Gregory W. Brown

University of North Carolina (UNC) at Chapel Hill - Finance Area

René M. Stulz

Ohio State University (OSU) - Department of Finance; National Bureau of Economic Research (NBER); European Corporate Governance Institute (ECGI)

Multiple version iconThere are 2 versions of this paper

Date Written: January 23, 2018

Abstract

Since 1965, average idiosyncratic risk (IR) has never been lower than in recent years. In contrast to the high IR in the late 1990s that has drawn considerable attention in the literature, average market-model IR is 44% lower in 2013-2017 than in 1996-2000. Macroeconomic variables help explain why IR is lower, but using only macroeconomic variables leads to large prediction errors compared to using only firm-level variables. As a result of the dramatic change in the number and composition of listed firms since the late 1990s, listed firms are larger and older. Larger and older firms have lower idiosyncratic risk. Models that use firm characteristics to predict firm-level idiosyncratic risk estimated over 1963-2012 can largely or completely explain why IR is low over 2013-2017. The same changes that bring about historically low IR lead to unusually high market-model R-squareds.

Keywords: Idiosyncratic risk, market risk, liquidity, firm age, firm size

JEL Classification: G10, G11, G12

Suggested Citation

Bartram, Söhnke M. and Brown, Gregory W. and Stulz, Rene M., Why Has Idiosyncratic Risk Been Historically Low in Recent Years? (January 23, 2018). Charles A. Dice Working Paper No. 2018-2; WBS Finance Group Research Paper. Available at SSRN: https://ssrn.com/abstract=3107798 or http://dx.doi.org/10.2139/ssrn.3107798

Söhnke M. Bartram

Warwick Business School - Department of Finance ( email )

Coventry, CV4 7AL
United Kingdom
+44 (24) 7657 4168 (Phone)
+1 425 952 1070 (Fax)

HOME PAGE: http://go.warwick.ac.uk/sbartram/

Gregory W. Brown

University of North Carolina (UNC) at Chapel Hill - Finance Area ( email )

Kenan-Flagler Business School
Chapel Hill, NC 27599-3490
United States

Rene M. Stulz (Contact Author)

Ohio State University (OSU) - Department of Finance ( email )

2100 Neil Avenue
Columbus, OH 43210-1144
United States

HOME PAGE: http://www.cob.ohio-state.edu/fin/faculty/stulz

National Bureau of Economic Research (NBER)

1050 Massachusetts Avenue
Cambridge, MA 02138
United States

European Corporate Governance Institute (ECGI)

c/o ECARES ULB CP 114
B-1050 Brussels
Belgium

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