Mutually Assured Education

Is Google Search a monopoly with gatekeeping power? Reg-ulators from the US, UK, and Europe have argued that it isbased on the assumption that Google Search dominates themarket for horizontal (a.k.a. “general”) web search. Googledisputes this, claiming that competition extends to all verti-cal (a.k.a. “specialized”) search engines, and that under thismarket definition it does not have monopoly power.In this study we present the first analysis of Google Search’smarket share under vertical segmentation of online search.We leverage observational trace data collected from a panelof US residents that includes their web browsing history andcopies of the Google Search Engine Result Pages they wereshown. We observe that participants’ search sessions begin atGoogle greater than 50% of the time in 24 out of 30 verticalmarket segments (which comprise almost all of our partic-ipants’ searches). Our results inform the consequential andongoing debates about the market power of Google Searchand the conceptualization of online markets in general