The Competition Appeal Tribunal (CAT) has published its decision to certify a class action brought by Professor Stephan against Amazon.

Professor Stephan’s claim alleges that Amazon engaged in a range of anticompetitive conducts to the detriment of c. 200,000 “third-party sellers” in the UK who use the Amazon marketplace to sell goods.

In its decision, the CAT described the expert economic report provided by Dr. Houpis as "comprehensive and very detailed," demonstrating strong endorsement of the analytical approach taken. The tribunal notably rejected most of Amazon’s criticisms regarding Dr. Houpis’ methodology.

Additionally, the CAT has certified a related class action led by Mr. Hammond, representing consumers who have made purchases through Amazon. The tribunal stated explicitly that “Mr Hammond will proceed as regards the … the exclusionary claim… on the basis of Dr Houpis methodology…”