Granular Instrumental Variables

93 Pages Posted: 15 Apr 2019 Last revised: 1 Aug 2019

See all articles by Xavier Gabaix

Xavier Gabaix

Harvard University - Department of Economics; National Bureau of Economic Research (NBER); Centre for Economic Policy Research (CEPR); European Corporate Governance Institute (ECGI)

Ralph S. J. Koijen

University of Chicago - Booth School of Business; Centre for Economic Policy Research (CEPR); National Bureau of Economic Research (NBER)

Date Written: July 30, 2019

Abstract

In many settings, there is a dearth of instruments, which hampers economists’ ability to investigate causal relations. We propose a quite general way to construct instruments: “granular instrumental variables” (GIVs). In the economies we study, a few large firms or countries account for a large share of economic activity. As they are large, their idiosyncratic shocks affect aggregate outcomes. This makes those idiosyncratic shocks valid instruments for aggregate shocks. We provide a methodology to extract idiosyncratic shocks from the data, this way creating GIVs. Those GIVs allow us to then estimate parameters of interest, including causal elasticities.
We first illustrate the idea in a basic supply and demand framework: we achieve a novel identification of supply and demand elasticities, based on idiosyncratic shocks to supply or demand. We then show how the procedure can be adapted to handle many enrichments. We provide initial illustrations of the procedure with two applications. First, we measure how “sovereign yield shocks” spill over to other countries in the Eurozone. Second, we estimate short-term supply and demand elasticities in the oil market. Our estimates match well existing estimates that use much more complex and labor-intensive (e.g., narrative) methods. We sketch how GIVs could be useful to estimate a host of other causal parameters in economics.

Suggested Citation

Gabaix, Xavier and Koijen, Ralph S. J., Granular Instrumental Variables (July 30, 2019). Available at SSRN: https://ssrn.com/abstract=3368612 or http://dx.doi.org/10.2139/ssrn.3368612

Xavier Gabaix

Harvard University - Department of Economics ( email )

Littauer Center
Cambridge, MA 02138
United States

National Bureau of Economic Research (NBER)

1050 Massachusetts Avenue
Cambridge, MA 02138
United States

Centre for Economic Policy Research (CEPR)

London
United Kingdom

European Corporate Governance Institute (ECGI)

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

Ralph S. J. Koijen (Contact Author)

University of Chicago - Booth School of Business ( email )

5807 S. Woodlawn Avenue
Chicago, IL 60637
United States

HOME PAGE: http://faculty.chicagobooth.edu/ralph.koijen/

Centre for Economic Policy Research (CEPR) ( email )

London
United Kingdom

National Bureau of Economic Research (NBER) ( email )

1050 Massachusetts Avenue
Cambridge, MA 02138
United States

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