Apple's data protection measure “App Tracking Transparency” (ATT) strengthens user privacy, but causes significant revenue losses in e-commerce, especially for small and medium-sized enterprises (SMEs). The reason for this is the mandatory opt-in for users introduced by ATT. This is shown by a study co-authored by Maximilian Kaiser from the University of Hamburg Business School. It will be published in Management Science in the coming weeks and is already available ahead of print online.
Since the introduction of ATT in April 2021, app providers in the iOS App Store have had to obtain additional consent from users before they can use tracking and advertising data. As through this Apple is systematically disadvantaging other market participants, the company was fined €150 million in France in the spring, and the German Federal Cartel Office is also investigating the case. However, it is not only advertisers who are affected, but also e-commerce companies that rely on them.
“The results show that Meta campaigns optimized for external conversions, i.e., purchases, achieved an average of 36.6% fewer clicks after the introduction of ATT,” said Maximilian Kaiser, co-author of the study and doctoral candidate at Prof. Michel Clement's Professorship of Marketing and Media at the University of Hamburg Business School. “This is directly attributable to the new opt-in rules.” Small providers in particular, who rely heavily on Meta data, saw up to 37.1% less revenue growth after the introduction of ATT compared to less dependent competitors. For Apple users, this could mean that offers will be less personalized in the future and online prices may be higher in order to offset the increased advertising costs.
For the empirical analysis, the research team drew on an extensive data set: An anonymized panel of 1,221 e-commerce companies provided weekly performance metrics on advertising campaigns on platforms such as Meta (Facebook/Instagram), Google, and TikTok, supplemented by device-specific sales data from 773 online retailers from the portfolio of Grips Intelligence, an e-commerce analytics platform of which Kaiser is the Director of Data Science.
“Well-intentioned data protection regulations can have unintended economic side effects, especially for data-intensive business models of small and medium-sized enterprises,” Kaiser sums up. His study shows that future measures must take greater account of the balance between privacy and fair competition in order not to disproportionately harm small players. The French competition authority has already used the findings to refute Apple's arguments that the introduction of ATT had no negative effect on advertisers (page 107, https://www.autoritedelaconcurrence.fr/sites/default/files/attachments/2025-07/2...)
The full study will be published soon in the renowned Management Science, is already available ahead of print online, and is based on international collaboration among co-authors Guy Aridor (Northwestern University), Yeon-Koo Che (Columbia University), Brett Hollenbeck (UCLA), Maximilian Kaiser (University of Hamburg Business School), and Daniel McCarthy (University of Maryland).
Maximilian Kaiser
University of Hamburg
University of Hamburg Business School
newsletter.bwl@uni-hamburg.de
Aridor, Guy, Che, Yeon-Koo, Hollenbeck, Brett, Kaiser, Maximilian, McCarthy, Daniel. (in Press 2025): Evaluating the Impact of Privacy Regulation on E-Commerce Firms: Evidence from Apple’s App Tracking Transparency. Management Science: https://pubsonline.informs.org/doi/10.1287/mnsc.2024.06600 . Preprint: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4698374
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