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Small screen, big echo? Estimating the political persuasion of local television news bias using Sinclair Broadcast Group as a natural experiment

  • Miho, Antonela
Publication Date
Oct 15, 2018
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We investigate the effect of biased local TV news on electoral outcomes using the quasi-random expansion of the U.S. media conglomerate: Sinclair Broadcast Group. We document Sinclair's pattern of bias to argue its local news programming exhibits a conservative slant since the 2004 election, though they have operated local TV stations since 1971. Using a DiD methodology through a dynamic two way fixed effect model, we argue that, conditional on a set of controls, the within county evolution of electoral outcomes would have been the same, absent the availability of a biased Sinclair major affiliate TV station. On average, we estimate that an extra year of coverage increases the presidential Republican two party vote share by .136% points within a county. Yet, we find no average effect across election years nor a complementary effect on voter turnout. We also consider the effect of Sinclair coverage by treatment cohort and given the partisan leaning of the county. Our estimates imply biased Sinclair news convinced 2.6-3.5% of its audience to vote Republican, depending on the sample considered. The totality of our results suggest that political persuasion is a dynamic process that takes time and that serves to entrench pre-existing beliefs. Our findings are robust to a series of checks, though a more precise definition of treatment may be helpful to increase the power of our strategy to detect an average global effect.

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