MEMORANDUM & ORDER Plaintiffs in this matter are credit and debit card users that do not and have not used American Express cards. They challenge, under state antitrust and consumer protection laws as a putative class action, the non-discrimination provisions that American Express and American Express Travel Related Services (together, “Amex”) impose on merchants that accept Amex cards as a payment method. Plaintiffs seek to certify two classes — credit card users and debit card users — on behalf of themselves and those similarly situated in eleven states for injuries alleged based on transactions at 38 enumerated retailers (“Qualifying Merchants”). (See Mot. for Class Cert. (Dkt. 138-2) at 3-6, 21.) Plaintiffs also seek to exclude the testimony of Amex’s expert, Dr. Eric Gaier, under Daubert v. Merrell Dow Pharms., Inc., 509 U.S. 579 (1993) and Fed. R. Evid. 702 and 401. (See generally Pl. Daubert Mot. (Dkt. 177-1).) Amex in tum seeks to exclude the testimony of Plaintiffs’ expert, Dr. Russell Lamb. (See generally Amex Daubert Mot. (Dkt. 170-1).) As detailed below, the Plaintiffs’ motion for class certification is GRANTED with respect to the state debit card classes and is DENIED with respect to the state credit card classes. Plaintiffs’ motion to exclude the testimony of Dr. Gaier is GRANTED in part and DENIED in part. Plaintiffs’ motion is GRANTED as it relates to testimony concerning offsets to class members from non-Qualifying Merchants and is DENIED for all other topics. Amex’s motion to exclude the testimony of Dr. Lamb is DENIED.1 I. BACKGROUND The court assumes general knowledge of the facts and procedural history of the long-running challenges to Amex’s non-discrimination provisions, also referred to as anti-steering provisions (“NDPs”). See, e.g., In re Am. Exp. Anti-Steering Rules Antitrust Litig. (In reAmex), No. 11-md-2221 (NGG), 2016 WL 748089, at *1-4 (E.D.N.Y. Jan. 7, 2016); Ohio v. Am. Express Co., 138 S. Ct. 2274, 2279-83 (2018); In re Am. Express Anti-Steering Rules Antitrust Litig., 361 F. Supp. 3d 324, 331 (E.D.N.Y. 2019). The challenges to Amex’s NDPs at one point included merchants, state attorneys general, and the U.S. Department of Justice as plaintiffs. In the present action, brought by putative class of non-Amex cardholding consumers, this court granted in part and denied in part Amex’s motions to dismiss and for judgment on the pleadings. (See Mot. to Dismiss Mem. & Order (Dkt. 43); Mot. for Judgment on the Pleadings Mem. & Order (Dkt. 63).) Plaintiffs are now proceeding under the antitrust laws of eleven jurisdictions2 and consumer protection laws of four states.3 (See generally Second Amend. Compl. (Dkt. 187).) Plaintiffs allege that Amex’s NDPs act as a vertical non-price restraint on trade in violation of state antitrust and consumer protection laws. (See id. 91, 159, 166-213.) Amex is a bank that operates a payment network for general purpose credit and charge cards (“credit cards”). (Id.
34-35.) Unlike its non-bank network competitors Visa and Mastercard, Amex operates a closed loop, meaning that it directly interacts with both consumers, by issuing cards, and with merchants, by contracting with them to accept Amex cards as a method of payment. (Id.
