Ulrich Matter

We study the impact of web search personalization on ideological segregation in search results. We deploy 150 synthetic internet users with randomized partisan browsing preferences across 25 US cities. These users are active during the US 2020 election and its aftermath. Daily experiments in which the users enter identical election-related queries provide strong evidence for ideological segregation in search results across locations with different partisan leanings but only limited evidence for ideological segregation within location across users with different partisan browsing habits. We discuss the important role of the national and local (online) media landscape for understanding these results.

We review conceptual and empirical contributions to the political economy of attention, with a focus on how attention allocation shapes political behavior and electoral accountability. The review distinguishes between endogenous (goal-directed) and exogenous (stimulus-driven) attention and examines how these concepts are incorporated into political economy models. We then discuss empirical research on how attention shifts – driven by media coverage, transparency reforms, and persuasive content – affect voting behavior and accountability outcomes. We also consider how digital technologies, such as algorithmic content curation and individual-level targeting, transform the political information environment and create new dynamics of attention allocation. The review concludes by outlining methodological approaches for identifying causal effects of attention and by highlighting key directions for future research in this growing field.