The authors thank Randy Bucklin, Nicholas Diebel, Michael Grubb, Brett Hollenbeck, Stephan Seiler, and Kenneth Wilbur for comments and suggestions. The authors have also benefited from the comments of seminar participants at University of Chicago Booth School of Business, Columbia University, Duke Fuqua, Harvard Business School, Rochester University, Stanford Graduate School of Business, University of California San Diego, the University of Wisconsin, and the 12th Workshop on the Economics of Advertising and Marketing. Any remaining errors are our own. Both authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or nonfinancial interest in the subject matter or materials discussed in this manuscript.