COVID-19 vaccines are widely available in wealthy countries, yet many people remain unvaccinated. Understanding the effectiveness -- or lack thereof -- of popular vaccination campaign strategies is therefore critical. In this paper, we report results from two studies that tested strategies...

In this paper, we investigate political communications in social networks characterized both by homophily-a tendency to associate with similar individuals-and group size. To generate testable hypotheses, we develop a simple theory of information diffusion in social networks with homophily and...

Throughout much of the developing world, politicians rely on political brokers to buy votes prior to elections. We investigate how social networks help facilitate vote-buying exchanges by combining village network data of brokers and voters with broker reports of vote buying. We show that...

Online reviews are a powerful means of propagating the reputations of products, services, and even employers. However, existing research suggests that online reviews often suffer from selection bias--people with extreme opinions are more motivated to share them than people with moderate...

In recent years, there has been widespread concern that misinformation on social media is damaging societies and democratic institutions. In response, social media platforms have announced actions to limit the spread of false content. We measure trends in the diffusion of content from 569 fake...

This paper studies information diffusion in social media and the role of bots in shaping public opinions. Using Twitter data on the 2016 E.U. Referendum ("Brexit") and the 2016 U.S. Presidential Election, we find that diffusion of information on Twitter is largely complete within 1-2 hours....

Substantial excitement currently exists in industry regarding the potential of using analytic tools to measure sentiment in social media messages to help predict individual reactions to a new product, including movies. However, the majority of models subsequently used for forecasting exercises...