Authors: Nicholas Hourigan & Joe Perkins
Class actions in the UK are starting to rival some of the largest U.S. cases, with both the number of claims and the sums involved nearing levels normally seen only in the United States. What seems more remarkable, though, is the dramatic rise in opt-out class actions in the UK and Europe – rare until recently. In 2023, 133 claims were filed in Europe, up 10% from 2022 and up 93% from 2019. Between 2018 and 2023, around €145 billion was sought in the UK – opt-in and opt-out – involving more than 540 million class members. 2023 saw more opt-out class actions than opt-in for the first time across Europe.[1]
The largest single damages award in Europe so far stands at €26.5 million – a modest sum compared with some other major cases. In the UK, more than 20 class actions are under way against several tech companies, pointing to ongoing growth in collective proceedings. Together, these UK claims exceed £30 billion. [2]
As well as the opt-out regime increasing the size and effect of potential claims, a UK Supreme Court decision in 2020 lowered the bar for certifying mass claims.[3] The case sets a precedent allowing collective actions to go ahead, even without precise individual loss assessments. Coupled with this, litigation funders have played their part, making it financially viable to bring large and complex claims.
Among the expertise needed in digital economy class actions, such as app store monopolies or digital advertising markets, forensic analysis and economic reasoning are central. Experts in these areas objectively test arguments to establish cause, prove liability and quantify damages. They also take prominent roles in carriage disputes and in parallel or overlapping claims.
Carriage Disputes and Parallel Claims
In a recent carriage dispute, the UK Competition Appeal Tribunal (“CAT”) decided between two competing applications to lead a collective action against an online marketplace platform for alleged abuse of dominance.[4] The CAT found that while both claims overlapped in scope, one in particular was “more suitable” to proceed. There were two decisive factors: the broader scope of the claim and, crucially, the “impressively well-developed and thought-through methodology” presented by the expert team.
The economic experts in this case proposed “re-running the algorithms” used by the platform to exclude the alleged abusive behaviour. This involves competition economics and data science, using techniques such as machine learning to construct an algorithm comparable to the platform’s recommendation system. In addition, the experts proposed a back-up methodology based on more traditional econometric approaches. The algorithmic approach will undoubtedly be challenging to carry out in practice. But courts have shown a willingness to accept cutting-edge methodologies when they may lead to improved estimates of harm.
Several other digital sector cases may follow more traditional methods, but these cases still often draw on both data science and competition economics expertise, given the vast datasets digital firms control. Forensic data experts are required to extract and analyse datasets on transactions, pricing and user behaviour. Economic experts develop and test models to estimate the effect of each company’s conduct on consumers and other businesses.
Economic analysis can clarify the likely damages for various potential claimant groups and show how different parts of a case affect one another. For example, pleading that pass-on is limited could help a defendant against one group of claimants but harm the defendant against another. The analysis can help clarify those trade-offs.
Both data science and economic analysis can provide the evidence needed to assess whether wrongdoing and harm have occurred. Competition economics then helps convert that evidence into legal and financial arguments about harm and liability.
When it comes to the rise in class actions, what do you need to think about? What actions do you need to take to prepare?
Pre-Action, Merits and Trial
At the pre-action and certification stage, the main tasks include identifying relevant data sources and defining who can be included in the class. Equally important is articulating how the alleged conduct caused loss to the class and the evidence needed to prove or disprove it. Engaging forensic experts at the start allows them to map, collect and preserve data – such as user data and transaction logs – while this digital evidence remains intact. Careful review then clarifies what is reliable, cutting the risks of oversights, such as missing or unreliable evidence that could weaken a case.
Economic experts develop models to estimate the scale and method of harm, clarifying whether the harm is common across the class. This exercise supports commonality analysis, making sure a case can be treated as a class action and that aggregate damages can be assessed, avoiding last-minute setbacks at certification.
Once a claim is certified and moves to the merits and discovery stage, forensic and economic experts focus on gathering and analysing evidence, establishing causation and modelling liability and damages. Earlier work would have uncovered patterns, anomalies or evidence of alleged misconduct. At this point, economic experts carry out econometric analysis to test hypotheses and quantify the effect of the alleged misconduct on the class, as well as estimate aggregate harm, overcharges or lost profits. This stage also entails considering counterfactual scenarios – answering what would have happened without the misconduct – and pass-on analysis, determining whether overcharges or losses were passed along to potential customers.
Trial and settlement calls on economic and forensic experts to serve as expert witnesses, testifying on how digital evidence was collected, analysed and interpreted. They also present complex technical material persuasively at hearings and in courts. Economic experts show the range of possible damages or outcomes, test opposing models and critique the methodologies, assumptions and conclusions of opposing experts, offering rebuttal evidence and testimony.
Other experts, such as valuation specialists and industry experts may also be crucial in particular cases, for instance where there are sector-specific issues. Examples include valuing intangible assets or adding context to technical evidence. Working with these experts minimises the risk of overlooking critical factors.
Claimants and Defendants
Forensic and economic expertise in digital economy class actions, whether for claimants or defendants, is broadly similar for both sides – robustly and independently analysing, measuring and challenging potential harms, as well as providing credible, evidence-based analysis of misconduct and its impact. But how and when each side engages with these experts differs.
For claimant-side lawyers, forensic and economic experts are indispensable for building a class-wide theory of harm, quantifying damages and establishing the commonality needed for class certification. Forensic data specialists make sure critical evidence is kept safe and data is strong enough to support certification. Economic experts then use this data to model the effect of the alleged conduct across the entire class, using advanced statistical and econometric techniques to test theories of harm and estimate aggregate damages.
On the defendant side, the same experts are tasked with stress-testing the claimant’s evidence, often in the context of a challenge to class certification. Forensic consultants scrutinise the data and methodologies presented by claimants, assessing whether there are flaws in data integrity, sampling and assumptions. They may uncover gaps or inconsistencies that undermine the claimant’s case.
Defendants also rely on their experts to consider alternative narratives – such as unrelated factors or the influence of competitive constraints – that could help explain market developments or show why any harms are limited.
Managing Risk and Evidence
The regulatory and reputational risks of class actions are huge. Engaging experts from the outset signals a company or claimant is serious about compliance and risk management. For defendants, the engagement can support internal investigations, inform voluntary disclosures and show transparency. For claimants, early expert input helps align litigation strategy with regulatory priorities – those under the EU Digital Markets Act or the UK Digital Markets, Competition and Consumers Act.
Preserving and analysing digital evidence before it is lost or overwritten is crucial, especially when relevant data may be temporary or spread across jurisdictions. Early expert input enables you to identify strengths and weaknesses and shape strategy. The more of this work you do upfront, the better prepared you will be. As a claimant-side legal team, you can then focus on claims with the strongest likelihood of success, while on the defendant-side you can identify and mitigate possible gaps before they become liabilities.
Success in digital economy class actions revolves around early joint working with outside experts. By avoiding silos, not underestimating complexity and maintaining clear, open communication, legal teams can build cases to withstand legal, regulatory and commercial scrutiny.
[1] Kenny Henderson, “Opt-out claims now dominate European class actions, CMS report reveals,” CMS (July 31, 2024) https://cms.law/en/gbr/news-information/opt-out-claims-now-dominate-european-class-actions-cms-report-reveals
[2] Francesca Micheletti and Jacob Parry, “Time was right for US Big Tech penalties, EU competition chief says,” Politico (April 23, 2025) https://www.politico.eu/article/time-right-united-states-tech-penalty-eu-competition-chief-teresa-ribera/
[3] Jonathan Speed, “Landmark Supreme Court decision takes an applicant-friendly approach to collective proceedings,” Bird & Bird (December 21, 2020) https://www.twobirds.com/en/insights/2020/uk/landmark-supreme-court-decision-takes-an-applicant-friendly-approach-to-collective-proceedings
[4] Katie Henderson, “Carriage dispute: Competition Appeal Tribunal finds in favour of Professor Stephan,” Mishcon de Reya (March 12, 2025) https://www.mishcon.com/news/carriage-dispute-competition-appeal-tribunal-finds-in-favour-of-professor-stephan
Authors:
Senior Managing Director, Leader of EMEA Data & Analytics
FTI Consulting
Nick Hourigan has over 20 years’ experience working on some of the largest investigations in recent history. He specializes in large volume, typically transaction-based, analytics for the financial services and other industries in litigation and investigation matters.
Nick has extensive experience in managing complex global-scale projects with record sets in the billions. His firm view is that the highest use of analytics is the elevation of expertise, and so his teams work in close collaboration with counsel, client and other FTI Consulting experts to ensure effective and efficient achievement of project objectives. Nick is an expert in developing innovative technical solutions to financial markets analyses which have been accepted by various regulatory authorities. Nick champions development of FTI Consulting’s Augmented Investigations® offering, whereby traditional analytics are complemented by data science and statistical methods in those – and, importantly, only those – situations where this coupling is to maximize client benefit.
Senior Managing Director
FTI Consulting
Joe Perkins is an expert economist with 20 years of experience as a professional economist in academia, consulting and government. Joe advises clients on regulatory and competition matters, with a focus on digital, energy and regulated utilities. He is an expert witness in several high-profile abuse of dominance and cartel cases in the UK and EU.
Before joining FTI, Joe worked as chief economist at the UK energy regulator Ofgem and as an economist at HM Treasury and the National Audit Office. He earned an M.Phil. in Economics with Distinction from Oxford University, where he was a prize fellow in economics at All Souls College. He is a Bye-Fellow in economics at Queens’ College, Cambridge, and publishes regularly in academic journals.