The Political Impact of Media Bias

In a representative system of government, policy outcomes are affected by the political preferences and the beliefs of the voters. The media play a key role in shaping these preferences and beliefs. They collect, summarize, and frame the information that voters use in their voting decisions. As a result, many have expressed concern that the media may be able to systematically manipulate political beliefs. Media slant may bias voters and thereby bias policy decisions. Concerns of this type are relevant in the United States (U.S.), given that over 70 percent of Americans believes that there is a great deal or a fair amount of media bias in news coverage (Pew 2004). Media bias is at least as common, if not more common, in countries with less media freedom than the U.S. Is media bias necessarily a problem? The effect of media bias depends on how the audience processes the information presented by the media. If the audience is aware of the media bias and fi lters it from the information, distortions in reporting are unlikely to have large effects on voter beliefs (Bray and Kreps 1987). In this rational world, media bias does not persuade voters. Alternate theories hold that media bias does persuade voters. This may occur because voters do not suffi ciently account for bias in the media (De Marzo, Vayanos, and Zwiebel 2003). This, in turn, may be a direct effect of the framing of the news (Lakoff 1987). Ultimately, understanding the impact of media bias on voter beliefs and preferences is an empirical task. In this chapter, we fi rst review some of the 6