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CEP discussion paper

Products and Productivity


Firms' decisions about which goods to produce are often made at a more disaggregate level than the data observed by empirical researchers. When products differ according to production technique or the way in which they enter demand, this data aggregation problem introduces a bias into standard measures of firm productivity. We develop a theoretical model of heterogeneous firms endogenously self-selecting into heterogeneous products. We characterize the bias introduced by unobserved variation in product mix across firms, and the implications of this bias for identifying firm and industry responses to exogenous policy shocks such as deregulation. More generally, we demonstrate that product switching gives rise to a richer set of industry-level dynamics than models where firm product mix remains fixed.


Andrew B. Bernard, Stephen Redding and Peter K. Schott

July 2005     Paper Number CEPDP0699

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This CEP discussion paper is published under the centre's Trade programme.