Online sources sometimes publish information that is false or intentionally misleading. We study the role of social networks and advertising on social networks in the dissemination of false news stories about childhood vaccines. We document that anti-vaccine Facebook groups disseminate false...

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...

We use anonymized and aggregated data from Facebook to explore the spatial structure of social networks in the New York metro area. We highlight the importance of transportation infrastructure in shaping urban social networks by showingthat travel time and travel costs are substantially stronger...

We use aggregated data from Facebook to show that COVID-19 was more likely to spread between regions with stronger social network connections. Areas with more social ties to two early COVID-19 "hotspots" (Westchester County, NY, in the U.S. and Lodi province in Italy) generally had more...

We model social media as collections of users producing and consuming content. Users value consuming content, but doing so uses up their scarce attention, and hence they prefer content produced by more able users. Users also value receiving attention, creating the incentive to attract an...

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...

We study how job-seekers share information about jobs within their social network, and its implications for firms. We randomly increase the amount of competition for a job and find that job-seekers are: (i) less likely to share information about the job with their peers; and (ii) choose to...

We document that the recent house price experiences within an individual's social network affect her perceptions of the attractiveness of property investments, and through this channel have large effects on her housing market activity. Our data combine anonymized social network information from...

We study why high-priced acquisitions of entrants by an incumbent do not necessarily stimulate more innovation and entry in an industry (like that of digital platforms) where customers face switching costs and enjoy network externalities. The prospect of an acquisition by the incumbent platform...