Sectoral comovement and conglomerate networks

Abstract We study the influence of multi-sector conglomerate firms on sectoral comovement. Using an innovative network model of firms and industries, we derive a novel measure of the co-concentration of industries in which two industries are more co-concentrated if they share greater exposure to the same conglomerate firms. Using time-series, cross-sectional, and longitudinal tests on establishment-level data from nearly all US firms over 1991 to 2019, we find that industries with higher co-concentration exhibit stronger comovement in employment, sales, and asset growth. Controlling for alternative explanations, a 1-SD increase in co-concentration corresponds to a 0.32-SD increase in the comovement of employment growth. In variance–covariance decompositions, we find that firm-specific shocks explain nearly half of aggregate volatility and industry comovement and that conglomerates play a significant role in sectoral comovement. Our framework helps explain how idiosyncratic, firm-level shocks contribute to aggregate fluctuations and influence business cycles.