Explaining the Drivers of Political Homophily in the United States

The next speaker in this Social Media & Society 2024 session is Abby Youran Qin, whose focus is on affective polarisation. She references the famous Adamic & Glance study that showed strong homophily between Republican and Democrat bloggers, respectively, and suggests that this can also be seen as an indication of affective polarisation.

Similarly, there is plenty of evidence of spatial polarisation in the United States, where certain states and counties are regarded as dominated by Republicans or Democrats; this points to a spatial sorting and geographic clustering of political partisans. How might we connect such individual-level homophily and place-level polarisation, then? The assumption here is that there is a feedback effect, where individual-level homophily leads to geographic sorting, and geographic sorting reinforces individual-level homophily.

This might be approached by calculating the theoretical likelihood of homophilic connections between any pair of counties based on their relative balance between Republicans and Democrats; 2020 election results per country might be used as data for this calculation, and offline mobility and online Facebook friendship data can then be used to hypothesise offline and online homophily values.

Such patterns can then be correlated with a variety of other socio-demographic indicators for each country (unemployment rate, poverty rate, racial diversity, education levels, media diversity, etc.). Overall, urban culture with large populations, robust local news, broad racial and ethnic diversity, and a progressive political culture tended to foster greater diversity in connectivity: better local news provision, local diversity, and the proportion of Democrat voters all tend to lower political homophily.