Models V. Markets: Does User Inertia Explain User Conduct in the Search Ecosystem?
Abstract
In the Google Search antitrust litigation, the district court relied on a behavioral-economics model of consumer irrationality in finding that default placements amplify users’ inertia bias and inhibit migration away from Google search to alternative providers despite negligible switching costs. This paper evaluates whether that proposition, and the underlying user-inertia assumption, withstands empirical scrutiny. While the user-inertia model has been endorsed by regulators and a significant portion of antitrust scholarship, a broad review of evidence from general search, specialized search, answer-engine and search-adjacent markets shows that it has difficulty accounting for the diverse range of user conduct in the search ecosystem. Users regularly multi-home across general search, specialized search, and answer-engine services and override defaults in search and other technology environments when they do not match user preferences. The user-inertia model also fails to account for Google’s inability to achieve adoption in specialized search markets, despite the use of default-like strategies, and Google’s currently lagging position in the answer engine market. Given the divergence between the user-inertia model and user conduct in the search landscape, I present and apply an alternative model of adaptively rational user choice, where default effects vary depending on multiple factors that impact decision costs, including task complexity, learning costs, data portability, choice reversibility, and multi-homing capacities. This model exhibits the best explanatory fit with variations in user conduct across search, search-adjacent, answer-engine, and other technology environments, rather than the prevailing model that assumes default settings uniformly lock in users and shield incumbent platforms from entry. This model also reflects more accurately the diverse range of empirical findings on the status quo bias and default effects in the social science literature on which behavioral antitrust scholarship ultimately relies.
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