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To Pool or Not to Pool: A Closer Look at the Use of Sub-Regressions in Antitrust Class Certification

Ai Deng
Journal of Competition Law & Economics
September 15, 2017

Did anticompetitive conduct impact all or nearly all class members? This question is central to a court’s class certification decision. And to answer the question, a methodology—known as sub-regressions—is being increasingly employed, particularly by defendants’ expert witnesses. A key step of a sub-regression type analysis is to partition the data into various sub-groups and then to examine data poolability. This article focuses on three areas of interest pertaining to sub-regressions: the related law and economics literature related to this methodology; courts’ recent class certification decisions in cases where parties introduced sub-regression analysis; and several methodological challenges, many of which have not been previously acknowledged, as well as potential ways to address them. The article emphasizes that a disciplined and rigorous implementation is crucial for the reliability of sub-regressions.