DMA in Effect and (In)Effective? Competition and Visibility in Online Product Search

Abstract Gatekeepers implement changes to their services in response to the Digital Markets Act. Whether the DMA regulation is not only in effect but also effective remains an open question. This article sheds light on the changes Google introduced to its search results page. We provide evidence on how these changes affect the visibility of competing comparison shopping services (CSS). Our analysis relies on data from over 1.2 million product-related searches. Our results point to a potential whack-a-mole challenge: on the one hand, we find a significant increase in the share of search results pages containing a CSS driven by a new CSS-unit. On the other hand, we document that Google simultaneously introduced another product-related element. As we will argue, this element functions as a Google-CSS and is rolled out more heavily and therefore better positioned than the new CSS-unit. The results are indicators of potential unequal treatment and highlight the need for enforcement. We emphasize that enforcement should pursue two objectives: (i) enabling the legitimate presence of vertically integrated services of the gatekeeper and (ii) ensuring the same opportunities for competitors. Importantly, promoting contestability requires that competitors are treated as independent rivals, not as part of the gatekeeper’s integrated service.