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J Gregory Sidak

J Gregory Sidak
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Who's Who Legal Consulting Experts: Economic Consulting - Competition Economists

Both an economist and a lawyer, J Gregory Sidak is the chairman of Criterion Economics and founding co-editor of the Journal of Competition Law & Economics, published quarterly by the Oxford University Press. He testifies as an expert economic witness throughout the Americas, Europe, Asia, and the Pacific.

Sidak’s antitrust engagements have concerned monopolisation, mergers, price fixing, market definition and market power, abuse of dominance, efficiency defences, and state-owned enterprises. He has three related areas of expertise as a testifying economic expert. First, he has testified extensively on damages and reasonable royalties for patent infringement, as well as FRAND royalties for standard-essential patents. Second, he has testified extensively on competition and contractual issues concerning regulated network industries and two-sided markets (telecommunications, the internet, credit cards, electricity, natural gas, transportation, and postal delivery), including asymmetric regulation, mandatory unbundling, access pricing, mobile termination rates, structural separation, line-of-business restrictions, spectrum policy and auctions, next-generation networks, net neutrality, stranded costs, and just compensation for regulatory takings or expropriation. Third, Sidak has advised or testified on behalf of parties facing questions on damages, valuation, pricing, or injunctive remedies in complex litigation, administrative proceedings, and international arbitration (including ICC, LCIA, PCA, WTO, and NAFTA arbitrations).

Sidak’s clients in matters of public record have included América Móvil, ATCO Gas, AT&T, Bell Canada, BT, Cable & Wireless, delfortgroup, Deutsche Telekom, Disney, eircom, Ericsson, Exelon, Google, Hitachi, KPN, Lamar Advertising, Microsoft, Nichia, Nippon Telegraph & Telephone, NTT DoCoMo, Panasonic, Portugal Telecom, Qualcomm, SoundExchange, Tata Communications, Telecom New Zealand, Telstra, the United Mexican States, UPS, Verizon, and Vodafone. In addition, he has twice served as Judge Richard Posner’s court-appointed neutral economic expert on damages, pursuant to US Federal Rule of Evidence 706, and as a consultant to the antitrust division of the US Department of Justice and the Competition Bureau of Canada.

Sidak’s amicus briefs have influenced the use of economic analysis in antitrust law. With Judge Robert Bork, Sidak successfully urged the Supreme Court of the United States in Pacific Bell Telephone v linkLine in 2008 to abolish the price squeeze as a theory of antitrust liability. In 2011, Sidak successfully urged Mexico’s competition authority to vacate a US$1 billion fine imposed on América Móvil for an alleged margin squeeze. In 2015, he filed with other economists an amicus brief in the Second Circuit in United States v American Express concerning market definition, market power, and competitive effects in the two-sided market for credit cards. The Second Circuit panel mentioned the amicus brief at oral argument and on its own motion the next day stayed the district court’s injunction against the disputed conduct by American Express.

Sidak received AB and AM degrees in economics and a JD from Stanford University. He was Judge Posner’s first law clerk. He later served on the senior staff of the Council of Economic Advisers in the Executive Office of the President and was deputy general counsel of the Federal Communications Commission.

Sidak has held the Ronald Coase Professorship of Law and Economics at Tilburg University in The Netherlands and the FK Weyerhaeuser Fellowship in Law and Economics at the American Enterprise Institute for Public Policy Research (AEI). While at AEI, he was also a senior lecturer at the Yale School of Management and taught courses with Dean Paul W MacAvoy on competitive strategy in telecommunications. Sidak was later a visiting professor at Georgetown University Law Center, where he taught antitrust law and telecommunications regulation. Before holding his academic appointments, Sidak practised law with Covington & Burling and O’Melveny & Myers and was a management consultant with the Boston Consulting Group.

Sidak has published six books and approximately 150 articles in scholarly journals and compilations, including the Antitrust Law Journal, the Columbia Law Review, the Journal of Competition Law & Economics, the Journal of Political Economy, the Stanford Law Review, the University of Chicago Law Review, and the Yale Law Journal. His essays have appeared in the New York Times, the Wall Street Journal, and many other newspapers. The Supreme Court of the United States first cited Sidak’s writings when he was 28 years old. The Supreme Court of Canada, the European Commission, and state supreme courts also have cited his writings, as have regulatory commissions and lower federal courts, including the US Court of Appeals for the DC Circuit in its 2001 Microsoft decision. Sidak has testified before Congress on multiple occasions. His articles and testimony in the public domain are available at

WWL says: Greg Sidak is praised for his “dedication to his work and for putting his clients’ best interests first”.

This biography is an extract from Who's Who Legal: Consulting Experts which can be purchased from our Shop.

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W11 1QQ, UK