Abstract
Abstract This paper examines the impact of data sharing among mobile apps, leveraging iOS’s policy that limits tracking users using identifiers. We find that this restriction decreases average new downloads by 3.96%. The effect is primarily driven by large apps that heavily rely on third-party data to acquire users (resulting in overlapping effects), and developers who lack first-party data (resulting in a lack of information advantage). However, new app introductions, particularly by first-time developers, decrease following the restriction, implying that large incumbent apps may gain increased dominance in the long run and offset their reduction in market concentration from user acquisition.