Does social media increase the consumption of ideologically congruent news and exacerbate polarization? I estimate the effects of social media news exposure by conducting a large field experiment randomly offering participants subscriptions to conservative or liberal news outlets on Facebook. I collect data on the causal chain of media effects: subscriptions to outlets, exposure to news on Facebook, visits to online news sites and sharing of posts, as well as changes in political opinions and attitudes. Four main findings emerge. First, random variation in exposure to news on social media substantially affects the news sites individuals visit. Second, exposure to counter-attitudinal news decreases negative attitudes toward the opposing political party. Third, in contrast to the effect on attitudes, I find no evidence that the political leaning of news outlets affects political opinions. Fourth, Facebook's algorithm is less likely to supply individuals with posts from counter-attitudinal outlets, conditional on individuals subscribing to them (a “ﬁlter bubble”). Together, these results suggest that social media algorithms are increasing polarization by limiting exposure to counter-attitudinal news.
Social movements are associated with large changes in norms and behavior, but evidence on their causal effects is limited. We study the effect of the MeToo movement on a high-stakes personal decision–reporting a sexual crime to the police. We construct a new dataset of sexual and non-sexual crimes in 24 OECD countries, covering 81 percent of the OECD population. We analyze the effect of the MeToo movement by employing a triple difference strategy over time, across countries and between crime types. We find that the movement increased reporting of sexual crimes by 14 percent during its first three months. While the effect slightly declines over time, the movement had a strong effect even 15 months after it started. We use more detailed US data to show that despite the increase in crimes reported, the movement did not increase the number of sexual crimes cleared by the police. In contrast to a common criticism of the movement, we do not find evidence for large differences in the effect across racial and socioeconomic groups. Our results suggest that social movements can rapidly change high-stakes personal decisions.