Brattle has been involved in numerous high-profile antitrust matters in the payment card industry, involving interchange fees, nondiscrimination rules, foreign transaction fees, dynamic currency conversion, and other practices. We have analyzed efficiency benefits and competitive effects resulting from these practices, developed models to identify the underlying conditions required for either anticompetitive or procompetitive behavior, assessed market performance (including firm profitability), provided statistical analyses relevant to defining relevant product markets, and evaluated alleged damages. Brattle economists recently supported American Express in its successful defense against antitrust claims made by the US Department of Justice and others involving its merchant agreements.