Sources of Media Bias

During presidential campaigns, the media plays an important role by providing background information on candidates to the general public. However, the media can be biased in favor of a specic candidate. This paper aims to investigates the source of media bias by estimating the eect of electoral competition on news coverage. If media bias is generated to cater to the major preferences in the media market, we should see more news coverage of the Republican candidate in markets where the majority of viewers is Republican. However, if the media bias comes from the motivation to impact the outcome of the election, we will see more media bias in media markets where the election is more competitive. In this paper, a simple model is constructed to explain how electoral competition aects media bias under the motivation to impact the election outcome. In the empirical analysis, media bias is measured by the relative length of presidential candidates’ sound bites in local TV news stories prior to the 2000 presidential election. The data shows that media bias is greater in media markets where the election is more competitive, which implies that media bias comes primarily from the desire to aect the election outcome.