This paper reviews the core legal test applied by the CAT for class certification in the two opt-out collective proceedings brought in the UK until now, and then considers the key economic issues at the heart of these cases.

It begins by describing the relevant legal test for certifying a class. It then moves to the main question it seeks to address: how rigorous can the Tribunal be in the context of an opt-out collective proceeding order (CPO) when there has been either no or only very limited disclosure prior to the hearing, and the goal of class certification procedures is to have shorter hearings held within months of the claim form being served. It also reviews the economics questions raised by both class certification cases:

In Mobility Scooters, the infringement was a vertical restriction related to the advertising of lower prices which affected seven out of 38 models of mobility scooters available in the market.

The main questions for the Tribunal at the certification stage was whether the claimants had a ‘common issue’. From an economics perspective, this meant looking into whether the overcharge only involved the retailers which were parties to the vertical agreement, or whether it was market-wide (i.e. the vertical restriction led to umbrella pricing): ‘Whether the umbrella sales experienced an overcharge was thus a central issue for quantification. This issue also played a role in the CPO application since the CAT was required to define the relevant claimant subclasses in the CPO and subsequently would be required to award any aggregate damages for each subclass.’ While the parties agreed a number of sub-classes based on distribution channels, the Tribunal did ‘not find those subclasses and what is within them sufficiently common.

In the collective proceedings against MasterCard, the author begins by reviewing various cases brought against MasterCard (which I already reviewed here and here). The discussion focuses on the counterfactuals chosen by the various courts – which is something which I have already covered in the posts mentioned above and elsewhere. As such, I am not going to rehash the issue here.

At a second stage, the author engages directly with the MasterCard CPO issue: whether all of the 46.2 million individual claims raised ‘common issues’ and were ‘suitable’ to be brought in collective proceedings. To address the challenges such a claim poses, the claimants’ expert submitted a methodology which attempted to arrive at a top-down estimate of the aggregate damages award calculated globally – which would lead to awards based on average individual loss.

However, as noted by the CAT: ‘The problem in the present case is that there is no plausible way of reaching even a very rough-and-ready approximation of the loss suffered by each individual claimant from the aggregate loss calculated according to the Applicant’s proposed method’. The Tribunal therefore decided that this kind of top-down approach can be   permissible but only if there is a reasonable and practicable means of getting back to the calculation of individual compensation


This is a clear, if somewhat descriptive exposition of the economic issues raised by the certification of opt-out claims. Even from a legal standpoint, it is quite sophisticated. While I nonetheless found myself in disagreement with the author, it is mainly on points that are not relevant for the purposes of this review.

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