Testing the Marketplace of Ideas
Daniel E. Ho, Frederick Schauer
Oliver Wendell Holmes’s notion of the marketplace of ideas—that the best test of truth is the power of an idea to get itself accepted in the competition of the market— is a central idea in free speech thought. Yet extant social science evidence provides at best mixed support for the metaphor’s veracity, and thus for the view that the truth of a proposition has substantial explanatory force in determining which propositions will be accepted and which not. But even if establishing an open marketplace for ideas is unlikely to produce a net gain in human knowledge, it may have other consequences. We illustrate how to empirically study the consequences of establishing or restricting a communicative domain. Our focus is on time, place, and manner restrictions, and we examine two potential natural experiments involving speech buffer zones around polling places and health care facilities providing abortions. Using a regression discontinuity design with geocoded polling information for over 1.3 million voters in two high-density jurisdictions (Hudson County and Manhattan), we provide suggestive evidence that speech restrictions in Hudson County reduced turnout amongst voters in the buffer zone. By failing to cue voters of the election, speech restrictions may have unanticipated costs. And using difference-in-differences and synthetic control matching with state-level data from 1973 to 2011, we illustrate how one might study the impact of speech restrictions around health care facilities. Although the evidence is limited, Massachusetts’s restrictions were accompanied, if anything, by a decrease in the abortion rate. Buffer zones might channel speech toward more persuasive forms, belying the notion that the cure for bad speech is plainly more speech.