The First-Order Approach to Merger Analysis

American Economic Journal: Microeconomics, Forthcoming

Harvard Economics Department Working Paper

32 Pages Posted: 20 Feb 2011 Last revised: 6 Apr 2013

See all articles by Sonia Jaffe

Sonia Jaffe

University of Chicago

E. Glen Weyl

Plural Technology Collaboratory, Microsoft Research Special Projects; Plurality Institute; GETTING-Plurality Research Network

Date Written: January 7, 2013


Using information local to the pre-merger equilibrium, we derive approximations of the expected changes in prices and welfare generated by a merger. We extend the pricing pressure approach of recent work to allow for non-Bertrand conduct, adjusting the diversion ratio and incorporating the change in anticipated accommodation. To convert pricing pressures into quantitative estimates of price changes, we multiply them by the merger pass-through matrix, which (under conditions we specify) is approximated by the pre-merger rate at which cost increases are passed through to prices. Weighting the price changes by quantities gives the change in consumer surplus.

Keywords: horizontal merger guidelines, comparative statics, local approximation

JEL Classification: D43, K21, L41

Suggested Citation

Jaffe, Sonia and Weyl, Eric Glen, The First-Order Approach to Merger Analysis (January 7, 2013). American Economic Journal: Microeconomics, Forthcoming, Harvard Economics Department Working Paper, Available at SSRN: or

Sonia Jaffe

University of Chicago ( email )

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Chicago, IL 60637
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Eric Glen Weyl (Contact Author)

Plural Technology Collaboratory, Microsoft Research Special Projects ( email )

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United States
8579984513 (Phone)


Plurality Institute ( email )

GETTING-Plurality Research Network ( email )

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Cambridge, MA 02138
United States

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