The Perils Of Antitrust Econometrics: Unrealistic Engel Curves, Inadequate Data, And Aggregation Bias

By Gabriel Lozada, University of Utah

Some economists argue antitrust policy should be based on empirical methods used by the Industrial Organization subdiscipline of economics, but non-economists must understand that those methods contain certain highly restrictive assumptions. Those assumptions involve econometric “identification,” and treating aggregate demand as if it were generated by a representative consumer (Muellbauer’s “generalized linear” preferences). We derive new results illustrating how restrictive the representative consumer assumption is; we explain aggregation bias in Almost Ideal Demand System models; and we show that data limitations make it even harder to justify economists’ restricting aggregate demands as one would the demand of a single individual.

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