This study investigates how homogeneous media consumption shapes political polarization by introducing a novel user-centered metric, Average Media Relatedness (AMR). Drawing on panel data from the Korea Media Panel Survey, we examine the extent to which individuals’ media repertoires exhibit internal similarity, and how this homogeneity relates to changes in political attitudes over time. Unlike traditional measures of selective exposure that rely on content typologies or platform categories, AMR quantifies media similarity based on co-usage patterns, offering a demand-side perspective on ideological isolation. Focusing on television, newspaper and selected online news outlets consumption in South Korea from 2012 to 2016, we analyze selective exposure patterns within traditional media environments. Our findings reveal a significant positive relationship between AMR and political polarization. Individuals who consume more topically or ideologically similar media content are more likely to exhibit increased polarization over time, even after controlling for sociodemographic variables. These results highlight the paradox of media abundance in high-choice media environments: while users enjoy more choice than ever before, their choices may foster narrower informational worlds. By situating this analysis in South Korea—a highly connected, media-saturated, yet politically divided society—this study contributes to global debates on how personalized media use can reinforce ideological divides. We discuss the implications of user-driven media insularity for democratic cohesion, and offer directions for mitigating polarization through media literacy and diversity-enhancing mechanisms.
Kim et al. (Thu,) studied this question.