The Impact of the General Data Protection Regulation (GDPR) on Online Tracking (2025),
International Journal of Research in Marketing, accepted, with Karlo Lukic and Bernd Skiera.
This study explores the impact of the General Data Protection Regulation (GDPR), introduced on May 25th, 2018, on online trackers—vital elements in the online advertising ecosystem. Using a difference-in-differences approach with a balanced panel of 294 publishers, we compare publishers subject to the GDPR with those unaffected (the control group). Drawing on data from WhoTracks.me, which spans 32 months from May 2017 to December 2019, we analyze how the number of trackers used by publishers changed before and after the GDPR. The findings reveal that although online tracking increased for both groups, the rise was less significant for EU-based publishers subject to the GDPR. Specifically, the GDPR reduced about four trackers per publisher, equating to a 14.79% decrease compared to the control group. The GDPR was particularly effective in curbing privacy-invasive trackers that collect and share personal data, thereby strengthening user privacy. However, it had a limited impact on advertising trackers and only slightly reduced the presence of analytics trackers.
Accepted at 2022 NBER Economics of Privacy Conference.
Economic Consequences of Online Tracking Restrictions: Evidence from Cookies (2024),
International Journal of Research in Marketing, 41 (2), 241-264, with Bernd Skiera.
In recent years, European regulators have debated restricting the time an online tracker can track a user to protect consumer privacy better. Despite the significance of these debates, there has been a noticeable absence of any comprehensive cost-benefit analysis. This article fills this gap on the cost side by suggesting an approach to estimate the economic consequences of lifetime restrictions on cookies for publishers. The empirical study on cookies of 54,127 users who received ~128 million ad impressions over ~2.5 years yields an average cookie lifetime of 279 days, with an average value of €2.52 per cookie. Only ~13% of all cookies increase their daily value over time, but their average value is about four times larger than the average value of all cookies. Restricting cookies’ lifetime to one year (two years) decreases their lifetime value by ~25% (~19%), which represents a decrease in the value of all cookies of ~9% (~5%). In light of the €10.60 billion cookie-based display ad revenue in Europe, such restrictions would endanger €904 million (€576 million) annually, equivalent to €2.08 (€1.33) per EU internet user. The article discusses these results' marketing strategy challenges and opportunities for advertisers and publishers.
Finalist IJRM Best Article Award 2024 (Top 3 Paper out of 41 published).
Finalist German Association of Business Research Best Paper Award 2024 (Marketing Section).
Covered by Computerworld, Cybernews, Horizont (in German), Digital Information World, Agenda Digitale (in Italian), Up Next Podcast (Adweek Best Marketing Podcast), Knowledge@HEC, IJRM Newsletter
How Does the Adoption of Ad Blockers Impact News Consumption? (2022),
Journal of Marketing Research, 59(5), 1002-1018. with Shunyao Yan, and Bernd Skiera.
Ad blockers allow users to browse websites without viewing ads. Online news publishers that rely on advertising income tend to perceive users’ adoption of ad blockers purely as a threat to revenue. Yet, this perception ignores the possibility that avoiding ads —which users presumably dislike—may affect users’ online news consumption behavior in positive ways. Using 3.1 million visits from 79,856 registered users on a news website, this research finds that ad blocker adoption has robust positive effects on the quantity and variety of articles users consume. Specifically, ad blocker adoption increases the number of articles that users read by 21.0%–43.2%, and it increases the number of content categories that users consume by 13.4%–29.1%. These effects are stronger for less-experienced users of the website. The increase in news consumption stems from increases in repeat visits to the news website, rather than in the number of page impressions per visit. These postadoption visits tend to start from direct navigation to the news website, rather than from referral sources. The authors discuss how news publishers could benefit from these f indings, including exploring revenue models that consider users’ desire to avoid ads.
Covered by Adguard, Dataskeptic.
A De-biased Direct Question Approach to Measuring Consumers' Willingness to Pay (2021),
International Journal of Research in Marketing, 38 (1), 70-84, with Reto Hofstetter, Harley Krohmer, and Z. John Zhang.
Knowledge of consumers' willingness to pay (WTP) is a prerequisite to profitable price-setting. To gauge consumers' WTP, practitioners often rely on a direct single question approach in which consumers are asked to explicitly state their WTP for a product. Despite its popularity among practitioners, this approach has been found to suffer from hypothetical bias. In this paper, we propose a rigorous method that improves the accuracy of the direct single question approach. Specifically, we systematically assess the hypothetical biases associated with the direct single question approach and explore ways to de-bias it. Our results show that by using the de-biasing procedures we propose, we can generate a de-biased direct single question approach that is accurate enough to be useful for managerial decision-making. We validate this approach with two studies in this paper.
How Do Consumer Characteristics Affect the Bias in Measuring Willingness to Pay for Innovative Products (2013),
Journal of Product Innovation Management, 30 (5), 1042-53, with Reto Hofstetter, Harley Krohmer, and Z. John Zhang.
Getting the price right is essential for successful new product introductions. An accurate estimate of consumers' willingness to pay is a crucial part of this task. Measurement of willingness to pay for innovations, however, often yields biased results. In this paper, we investigate consumer-related characteristics and motives that might underlie this bias. Drawing on the elaboration likelihood model, we develop a conceptual model to identify consumer characteristics relevant for preference measurement for innovative products. In doing so, two main factors that potentially influence hypothetical bias are distinguished: ability and motivation. Our conceptual discussion and empirical results demonstrate that the validity of willingness to pay statements is higher among consumers who show a high ability to assess the new product's utility and who are truly interested in purchasing the new product. Counter to intuition, willingness to pay statements from innovators, consumers with good product category knowledge, or consumers who perceive the new product to be highly innovative are relatively more biased and should be interpreted with caution. This research is among the first to look at consumer characteristics rather than methodological issues when it comes to measuring consumer willingness to pay for innovative products. Our conceptual discussion and empirical examination of the drivers of hypothetical bias can be used to refine the validity of the results of the direct willingness to pay approach. These findings should help improve new product pricing surveys and open new avenues for research in measuring consumer preferences.
How Should Consumers' Willingness to Pay Be Measured? An Empirical Comparison of State-of-the-Art Approaches (2011),
Journal of Marketing Research, 48 (1), 172-184., with Reto Hofstetter, Harley Krohmer, and Z. John Zhang.
This study compares the performance of four commonly used approaches to measure consumers’ willingness to pay with real purchase data (REAL): the open-ended (OE) question format; choice-based conjoint (CBC) analysis; Becker, DeGroot, and Marschak's (BDM) incentive-compatible mechanism; and incentive-aligned choice-based conjoint (ICBC) analysis. With this five-in-one approach, the authors test the relative strengths of the four measurement methods, using REAL as the benchmark, on the basis of statistical criteria and decision-relevant metrics. The results indicate that the BDM and ICBC approaches can pass statistical and decision-oriented tests. The authors find that respondents are more price sensitive in incentive-aligned settings than in non-incentive-aligned settings and the REAL setting. Furthermore, they find a large number of “none” choices under ICBC than under hypothetical conjoint analysis. This study uncovers an intriguing possibility: Even when the OE format and CBC analysis generate hypothetical bias, they may still lead to the right demand curves and right pricing decisions.
How Does Disabling Cookie Tracking Impact Online News Consumption? (2024), with Yufei Shen (Nova) and Xitong Li (HEC), Conference on Information Systems and Technology (CIST), Seattle, United States.
How Does Disabling Cookie Tracking Impact Online News Consumption? (2024), with Yufei Shen (Nova) and Xitong Li (HEC), International Conference on Information Systems (ICIS), Bangkok, Thailand.
Sophisticated Consumers with Inertia: Long-Term Implications from a Large-Scale Field Experiment, with Avner-Strulov Shlain (Chicago) and Navdeep Sahni (Stanford), Revise and Resubmit, American Economic Review.
Using a randomized eld experiment with a leading European newspaper, we study both the inertia anticipated by consumers and the actual inertia they experience. Our experiment among two million readers varies promotional subscription terms, including whether or not the contract automatically renews to a full-price subscription by default. By analyzing their subscription behavior over two years, we study how consumers respond to inertia-inducing subscription contracts in the short- and long-run. We find strong inertia. Half of the auto-renewal contract takers continue to a full-price subscription while rarely using it. At the same time, consumers preempt their future inertia; 24%-36% of potential subscribers avoid subscribing when offered an auto-renewal promo. Further, offering an auto-renewal contract decreases the share of subscribers over the two years after the promo by 10%. Even though auto-renewal generates higher revenue in the medium-run due to payments from inert subscribers, auto-renewal and auto-cancel are revenue equivalent after one year, but with fewer subscribers in auto-renewal. Using a mixed-types model, we estimate that while 70% of consumers are inert, a large majority of them (at least 58%) are aware of their inertia. Our results highlight the importance of sophistication about future biases in the market; sophisticated consumers avoid exploitation and are missed by researchers and firms analyzing only takers, since takers are selected on their naivete.
Accepted at 2023 NBER Winter IO and QME Conference.
Covered by Stanford Insights , Becker Friedman Institute, Chicago Booth Review, Knowledge@HEC, The Conversation, Futurity
The Economic Value of User Tracking for Publishers, with Rene Laub (Goethe) and Bernd Skiera (Goethe).
Regulators and browsers increasingly restrict user tracking to protect users’ privacy online. In two large-scale empirical studies, we study the economic implications for publishers relying on selling advertising space to finance their content. In our first study, we draw on 42 million ad impressions from 111 publishers covering EU desktop browsing traffic in 2016. In our second study, we use 218 million ad impressions from 10,526 publishers (i.e., apps) covering EU and US mobile in-app browsing traffic in 2023. The two studies differ in the share of trackable users (Study 1: 85%; Study 2: Apple: 17%, Android: 91%). Still, we find similar average ad impression price decreases (Study 1: 18% and Study 2: 23%) when user tracking is unavailable. More than 90% of the publishers realize lower prices when selling ad impressions for untrackable users. Publishers offering content on sports, cars, lifestyle & shopping, and news & information suffer the most. Premium publishers with high-quality edited content and strong reputations, thematic-focused (niche) publishers, and smaller publishers suffer less from the unavailability of user tracking. In contrast, non-premium publishers with non-edited or user-generated content, thematic-broad (general news) publishers, and larger publishers suffer more. The availability of a user ID generates the highest value for publishers, whereas collecting a user’s browsing history, perceived as intrusive by most users, generates only a small value for publishers. These results affirm that ensuring user privacy online has substantial costs for online publishers, but those costs differ across publishers and the type of collected data. This article offers suggestions to reduce these costs.
The Impact of the General Data Protection Regulation (GDPR) on Online Usage Behavior, with Julia Schmitt (Goethe) and Bernd Skiera (Goethe).
Privacy regulations often necessitate a balance between safeguarding consumer privacy and preventing economic losses for firms that utilize consumer data. However, little empirical evidence exists on how such laws affect firm performance. This study aims to fill that gap by quantifying the impact of the European Union’s General Data Protection Regulation (GDPR) on online usage behavior over time. We analyzed data from 6,286 websites across 24 industries, covering 10 months before and 18 months after the GDPR’s enactment in 2018. Employing a generalized synthetic control estimator, we isolated the short- and long-term effects of the GDPR on user behavior. Our results show that the GDPR negatively affected online usage per website on average; specifically, weekly visits decreased by 4.88% in the first 3 months and 10.02% after 18 months post-enactment. At the 18-month mark, these declines translated into average revenue losses of about $7 million for e-commerce websites and nearly $2.5 million for ad-based websites. Nonetheless, the GDPR’s impact varied across website size, industry, and user origin, with some large websites and industries benefiting from the regulation. Notably, the largest 10% of websites pre-GDPR suffered less, suggesting that the GDPR has increased market concentration.
The Sources of Researcher Variation in Economics , with Nick Huntington-Klein (Seattle University), Claus Poertner (Seattle University), et al..
We use a rigorous three-stage many-analysts design to assess how different researcher decisions—specifically data cleaning, research design, and the interpretation of a policy question—affect the variation in estimated treatment effects. A total of 146 research teams each completed the same causal inference task three times each: first with few constraints, then using a shared research design, and finally with pre-cleaned data in addition to a specified design. We find that even when analyzing the same data, teams reach different conclusions. In the first stage, the interquartile range (IQR) of the reported policy effect was 3.1 percentage points, with substantial outliers. Surprisingly, the second stage, which restricted research design choices, exhibited slightly higher IQR (4.0 percentage points), largely attributable to imperfect adherence to the prescribed protocol. By contrast, the final stage, featuring standardized data cleaning, narrowed variation in estimated effects, achieving an IQR of 2.4 percentage points. Reported sample sizes also displayed significant convergence under more restrictive conditions, with the IQR dropping from 295,187 in the first stage to 29,144 in the second, and effectively zero by the third. Our findings underscore the critical importance of data cleaning in shaping applied microeconomic results and highlight avenues for future replication efforts.
Consumers' Perceived Privacy Violations in Online Advertising, with Kinshuk Jerath (Columbia Business School).
Accepted at FTC PrivacyCon 2024 and CNIL Privacy Research Day 2024.
Covered by Datagrail, Ad Exchanger, Cornerstone Research
Paying for Privacy: Pay-or-Tracking Walls, with Timo Mueller-Tribbensee (Goethe University), and Bernd Skiera (Goethe University).
Accepted at FTC PrivacyCon 2024.
Covered by Law.com
Privacy and the Prevalence of Inconsistencies in Third-Party Consumer Profiling, with Lennart Kraft (Goethe), Nico Neumann (Melbourne Business School), and Bernd Skiera (Goethe).
2025: European Quant Marketing Workshop, Indian Institute of Management Bangalore (IIMB), Boston University Online Research Seminar on Digital Business*, Production and Operations Management Society (POMS) Conference *, Paris Conference on Digital Economics, Workshop on the Economics of Advertising and Marketing Tallinn (Estonia).
2024: Digital Platforms Working Group, Paris Dauphine University, Digital Economics Workshop Rotterdam*, University of Maastricht, Marketing Science Conference*, FTC PrivacyCon, Behavioral IO and Marketing Symposium (BIOMS)*, European Marketing Academy Conference (EMAC) Bucharest (Romania), Marketing Theory + Practice (TPM) Conference*, ZEW Conference on Information and Communication Technologies (ICT), Statistical Challenges in Electronic Commerce Research (SCECR), CNIL Privacy Research Day, Chuo University Tokio*, Goethe University Frankfurt*, YES Marketing Conference Basel (Switzerland), Weizenbaum Institute Berlin, INRIA BALANCE Workshop French Riviera (France)*, Conference on Information Systems and Technology (CIST) Seattle (USA)*, International Conference on Information Systems (ICIS) Bangkok (Thailand)*.
2023: Digital Economics Workshop Lausanne, ...
Ad-hoc reviewer for Nature, Management Science, Marketing Science, Information Systems Research, Journal of the Academy of Marketing Science, International Journal of Research in Marketing, European Journal of Operational Research, Journal of Behavioral and Experimental Economics, Journal of Interactive Marketing, Food Policy, Economic Inquiry, Schmalenbach Journal of Business Research, Journal of Business Economics, International Journal of Internet Marketing and Advertising, Marketing Review Sankt Gallen, Swiss Journal of Business Research and Practice, Business Administration Review.
Ad-hoc reviewer for Israel Science Foundation, German National Science Foundation, Swiss National Science Foundation.