Quantifying the Scope for Efficiency Defense in Merger Control: The Werden-Froeb-Index

Abstract

In both US and EU merger control, merger-specific efficiencies are recognized as a possible defense for horizontal mergers that raise competition concerns. We introduce the Werden-Froeb-index (WFI) to assist in evaluating these efficiencies. The index measures the average reduction in marginal costs required to restore pre-merger equilibrium prices and quantities after the merger is consummated. It has low information requirements and can deal with any number of firms in price- or quantity-competition merging fully or partially, and a large class of demand and cost functions. We show how the WFI complements Phase I merger inquiries as a screening mechanism.