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The Commensurability Myth in Antitrust

Posted by on Friday, January 15, 2016 in Articles, Volume 69, Volume 69, Number 1, Volumes.

The Commensurability Myth in Antitrust


Modern antitrust law pursues a seemingly unitary goal: competition. In fact, competition—whether defined as a process or as a set of outcomes associated with competitive markets—is multifaceted. What are offered in antitrust cases as procompetitive and anticompetitive effects are typically qualitatively different, and trading them off is as much an exercise in judgment as mathematics. But despite the inevitability of value judgments in antitrust cases, courts have perpetuated a commensurability myth, claiming to evaluate “net” competitive effect as if the pros and cons of a restraint of trade are in the same unit of measure. The myth is attractive to courts because it appears to allow the law to avoid the murky, value-laden compromises struck by other areas of regulation. But courts have suppressed important debates about what matters most about competition by glossing over the fact that even given a narrow mandate—to protect competition—antitrust law must make contested value judgments. Debunking the commensurability myth is the first step in stimulating scholarly and judicial debates about how to balance antitrust’s inherent tradeoffs, such as price effects with qualitative consumer welfare, present with future benefits from competition, and consumer welfare among different classes of purchasers.

This Article explores the commensurability myth, using Sherman Act § 1 cases to illustrate the incommensurability of most pro- and anticompetitive effects claimed in an antitrust suit. It then argues that the myth distorts antitrust litigation as courts find ways—such as insurmountable burdens of proof—to avoid the appearance of incommensurate balancing. Finally, it identifies the doctrinal and institutional debates—largely missing from antitrust discourse today—raised by confronting the commensurability problem in antitrust.


Associate Professor of Law, Vanderbilt Law School; J.D., Harvard Law School; M.Phil, University of Cambridge; B.A., Yale University. Thank you to Darren Bush, Edward Cheng, Luke Froeb, Scott Hemphill, and the participants at the Yale/Harvard/Stanford Junior Faculty Forum for helpful comments on a previous draft. Thank you to Chastity Bobo, Zachary Hebert, and Sean Ryan for excellent research assistance.