Smartphones and Polarization: Cross-Country Evidence

This paper examines whether the rise of smartphone-enabled social media is associated with political polarization across countries. The empirical strategy exploits the timing of a major technological transition: mobile phones became politically consequential not simply as communication devices, but when smartphones and mobile social media made online interaction continuous, personalized, and algorithmically curated. Consistent with this interpretation, two-way fixed-effects estimates show that the association between mobile-phone subscriptions and polarization turns positive after the early-2010s smartphone transition, especially before mobile-subscription saturation and in countries with higher internet use. Complementary staggered difference-in-differences estimates indicate higher polarization after countries cross a mass mobile-diffusion threshold, with little evidence of pre-treatment divergence. The main analysis uses annual Varieties of Democracy (V-Dem) polarization data for 176 countries from 2000 to 2024, and separately, a polarization measure constructed from the World Values Survey. An agent-based model illustrates how engagement-oriented content selection can amplify cultural divisions. World Values Survey estimates using an aggregate Kullback–Leibler polarization measure point in the same direction.