User self-selection is the dominant filter determining content consumption on Facebook, though the 5-8 percent algorithmic reduction in cross-cutting content does not directly bound the affective polarization impact because the hostility dimension of marginal content may matter more than ideological balance.
Bakshy, Messing, and Adamic (2015) measured ideological exposure among 10.1 million US Facebook users and found that individual choice had a stronger role than algorithmic ranking in limiting cross-cutting content exposure.
Users' click-through choices reduced cross-cutting content consumption by 17% for conservatives and 6% for liberals, while algorithmic ranking reduced it by approximately 5-8%.
Eady et al. (2019) found that most US Twitter users are exposed to substantial cross-cutting political content and only a small minority live in tight echo chambers.
Are there other events or causes that could account for the presence of the sign?
What is the strength of the correlation between the sign and the event/state it is taken to indicate?
Has the sign actually been observed reliably in this case?