An Empirical Study of the Multifactor Tests for Trademark Infringement

The thirteen circuits' thirteen different multifactor tests for the likelihood of consumer confusion have long played a role of central importance in American trademark litigation, yet they have received little academic attention and no empirical analysis.Courts, commentators, and practitioners have all the while speculated about which factors, if any, drive the outcome of the tests, how the factors interact, and, most importantly, whether the circuits' different tests, given the same facts, would yield different outcomes.With a view to the settling of these questions and ultimately to the reform of the multifactor tests, this Article sets forth the results of an empirical study of all reported federal district court opinions for the five-year period from 2000 to 2004 in which a multifactor test for the likelihood of consumer confusion was used.In the process, it presents the multifactor test for the likelihood of consumer confusion as an ideal case study in legal multifactor decision making and develops a methodology and theoretical toolkit for the study of this form of legal analysis across the many areas of law that employ multifactor tests.Working from an original data set of 331 opinions, this Article finds significant variation among the circuits in the application and outcome of their respective tests.Drawing upon recent social science learning on cognition and decision making, it further shows that judges employ 'fast and frugal" heuristics to short-circuit the multifactor analysis.A few factors prove to be decisive; the rest are at best redundant and at worst irrelevant.