We study the impact of the implementation of Apple’s App Tracking Transparency (ATT) framework on the Apple App Store ecosystem. We use comprehensive data on every app available in both the Apple App Store and Google Play Store ecosystems in the one year period around the implementation of ATT, and a difference in differences analysis to investigate whether the introduction of the privacy transparency framework affected the incentives for developers in the Apple ecosystem to create new apps, update their existing apps, or withdraw from the market. We also leverage data on the presence of Software Development Kits (SDK) in a select number of apps in each ecosystem to study how developers adapted specific functionalities in their products, such as the use of advertising platforms or payment systems. We find that the number of available apps in the Apple App Store ecosystem quickly recovers after an initial drop following the introduction of ATT. We do not find evidence suggesting that ATT has reduced developers’ interest in the Apple ecosystem relative to the Google ecosystem. When analyzing the use of SDKs by apps in genres that rely heavily on advertising before ATT, we find a reduction in the use of Ad Mediation SDKs, and, an increase in the use of authentication and payment SDKs. Our results suggest developers did not withdraw from the market after ATT and instead adapted to operate under the conditions of a more protective privacy framework.
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