Distorting the News? The Mechanisms of Partisan Media Bias and Its Effects on News Production

Abstract

Integrating scholarship from several fields of study, this paper proposes a new model for understanding how partisan bias operates and how to measure its effects. We chart the factors that influence partisan bias over news production within news organizations that are simultaneously constrained and conditioned by factors of market competition, context considerations and journalistic norms. We argue that partisan media bias of a news-story is expressed in the manner that different news outlets cover the same political story within the same timeframe relative to one another. We find that description bias is a key parameter that is intertwined with selection bias mechanisms that highlight and downplay news items according to their content. We illustrate how partisan media coverage occurs in the context of a major political protest in Israel. We employ a dataset consisting of 1556 news products from all major newspapers. We find that partisan bias finds its strongest expression in the types of news products that the news outlets emphasize on their front-page and in the sizing of articles. These mechanisms of partisan bias can be generalized in the study of partisan bias in other types of news outlets.