Chapter 15. Empirical Studies of Media Bias

In this chapter we survey the empirical literature on media bias, with a focus on partisan and ideological biases. First, we discuss the methods used to measure the relative positions of media outlets. We divide bias into two categories, explicit and implicit bias. We group existing measures of implicit bias into three categories: measures based on comparing media outlets with other actors, measures based on the intensity of media coverage, and measures based on tone. In the second part of the chapter we discuss the main factors that are found to be correlated with media bias, dividing these into demand-side and supply-side factors. We also discuss the role of competition across media outlets. In the third part of the chapter we discuss some of the attempts to measure the persuasive impact of media bias on citizens’ attitudes and behavior.