In this paper, I attempt to provide a comprehensive review of the evidence regarding the relationship between political polarization in the US and internet use. In the first part, I examine whether there has indeed been a rise in political polarization in the US in the last several decades. The remaining second and third parts deal with the relationship between polarization and internet use. I begin, in the second part, by reviewing evidence pertaining to the question of whether internet use plays a causal role in bringing about polarization. I then move, in the third part, to exploring the possible means by which internet use might bring about polarization. By analogy to cigarettes and cancer, the second part examines whether cigarette smoking causes cancer, while the third part examines how cigarette smoking causes (or might cause) cancer. One focus, in the third section, is on the most often discussed mechanism of internet-caused polarization: segregated information exposure, which corresponds to claims that polarization is driven by an internet ecosystem characterized by “echo chambers”, “filter bubbles”, and otherwise partisan information consumption and dissemination.The brief summary for each of the three parts is this. First, there is evidence that polarization has been on the rise in the U.S. in the recent decades—but it depends what you measure. When comparing Republican and Democrats, there is strongest evidence for increases in affective polarization and policy-based polarization. Second, most analyses would marshal against a version of reality where the rise in the political polarization in recent decades is mostly accounted for by the dramatic rise in internet use over this same time period. However, one notable, well-conducted, large-scale randomized direct intervention study confirms that de-activating a social media account (Facebook) resulted in significant and non-trivially sized decreases in polarization, specifically related to political opinions and policy preferences (Allcott, Braghieri, Eichmeyer, & Gentzkow, 2019). Finally, the evidence is murkiest regarding how internet use might drive polarization. With regard to polarization via segregated information exposure, claims that partisans inhabit wildly segregated “echo chambers” or “filter bubbles” are largely overstated. Nevertheless, there are significant and meaningful differences in the political content that partisans of different political orientations consume online, comparable to the degree of segregation in national print newspaper readership. Causal evidence linking this differential exposure to political polarization is not as strong as evidence that differential exposure exists. Evidence for other mechanisms of polarization is suggestive but awaits strong empirical confirmation.
Correction for Boxell et al., Greater Internet use is not associated with faster growth in political polarization among US demographic groups
