A Primer on AIDS-Based Models in Antitrust Analysis

This article is available at European Competition Journal 10(1), April 2014, pp. 123-153(31)

31 Pages Posted: 2 Feb 2013 Last revised: 11 Dec 2015

Shawn W. Ulrick

U.S. Federal Trade Commission (FTC)

Date Written: January 31, 2013

Abstract

The purpose of this paper is to provide an introduction to AIDS-based demand systems (i.e., those based on Deaton and Muellbauer's Almost Ideal Demand System). We discuss derivation of the AIDS model from its microeconomic foundations, clearly state the assumptions underlying AIDS, and provide a primer on how to implement the model in practice. We use a high level of detail to show every step of the AIDS process. We detail the algebra because the original articles by either Deaton and Muellbauer (in 1980) or Hausman et al. (in various papers over several years) skip most of the steps. We discuss using the AIDS model by itself and in two variations of Hausman et al.’s multilevel systems. We briefly discuss some pitfalls common to all demand systems. Finally, at the end of this document, we provide an example of how the elasticities may be used to predict post-merger price changes via a linear approximation to the Bertrand model.

Keywords: AIDS, Almost Ideal Demand System, Demand Estimation, Merger Simulation, elasticities

Suggested Citation

Ulrick, Shawn W., A Primer on AIDS-Based Models in Antitrust Analysis (January 31, 2013). This article is available at European Competition Journal 10(1), April 2014, pp. 123-153(31). Available at SSRN: https://ssrn.com/abstract=2210072 or http://dx.doi.org/10.2139/ssrn.2210072

Shawn W. Ulrick (Contact Author)

U.S. Federal Trade Commission (FTC) ( email )

600 Pennsylvania Ave., NW
Washington, DC 20580
United States

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