Full Citation

Title: Shift-Share Designs: Theory and Inference

Citation Type: Journal Article

Publication Year: 2019

ISBN:

ISSN: 0033-5533

DOI: 10.1093/qje/qjz025

NSFID:

PMCID:

PMID:

Abstract: We study inference in shift-share regression designs, such as when a regional outcome is regressed on a weighted average of sectoral shocks, using regional sector shares as weights. We conduct a placebo exercise in which we estimate the effect of a shift-share regressor constructed with randomly generated sectoral shocks on actual labor market outcomes across U.S. commuting zones. Tests based on commonly used standard errors with 5% nominal significance level reject the null of no effect in up to 55% of the placebo samples. We use a stylized economic model to show that this overrejection problem arises because regression residuals are correlated across regions with similar sectoral shares, independent of their geographic location. We derive novel inference methods that are valid under arbitrary cross-regional correlation in the regression residuals. We show using popular applications of shift-share designs that our methods may lead to substantially wider confidence intervals in practice.

Url: https://academic.oup.com/qje/article/134/4/1949/5552146

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Authors: Adão, Rodrigo; Kolesár, Michal; Morales, Eduardo

Periodical (Full): The Quarterly Journal of Economics

Issue: 4

Volume: 134

Pages: 1949-2010

Data Collections: IPUMS USA

Topics: Labor Force and Occupational Structure, Other

Countries: