research

There is increasing evidence that social media is detrimental to mental health and self-esteem. A puzzle is why, in spite of this, people join these platforms. One possibility is that people feel compelled to participate: they dislike these networks—in particular, the way in which they generate rat races—but they need to be on them to socialize with peers. We refer to networks that harm users as “bad networks”. We model settings with network externalities and show that, surprisingly, bad networks are easy to establish. We also show that networks tend to be both bad and easy to establish when they create rat races—as social networks often do. Amplifying the rat race boosts network size which, while harmful to consumers, may benefit the platform.

A sender wishes to persuade a group of receivers but can only communicate with one target receiver. The target’s actions, in turn, may influence others. Who should she target? How should she customize her communication? The sender optimally customizes communication to the target as if other receivers did not exist and trades off popularity against influence: she may optimally target less popular receivers. We characterize a measure of a target’s market influence that the sender maximizes and show that, in large markets, she strictly prefers less customizable communication if the market is more polarized or if high-popularity influencers are rare.

A growing body of empirical evidence reveals a fundamental asymmetry in the diffusion of social behaviors: prosocial behaviors often exhibit strategic substitutability (“bystander effects”), while antisocial behaviors exhibit strategic complementarities (“licensing effects”). Moreover, even a single behavior (e.g., protest participation) can be a complement in some settings and a substitute in others. To unify these findings, we develop a model of strategic diffusion on networks with positive (prosocial) or negative (antisocial) spillovers. Our results rely on a novel conception of influence, capturing the causal impact of an individual’s adoption on others. Prosocial behaviors are complementary in sparse networks but substitutable in dense ones, while antisocial behaviors exhibit the reverse pattern. Our model predicts that prosocial behaviors emerge continuously, while antisocial behaviors exhibit a discontinuous, sudden emergence. Effective policies can target the network density or perceptions of the extent of spillovers to encourage prosocial behaviors and inhibit antisocial ones.

Governments often restrict communication to prevent people from coordinating protests and popular uprisings. But communication is also essential to economic activity, which creates a tradeoff for governments. We build a theoretical model to study this tradeoff. Our model shows: (i) how and why large protests occur suddenly, (ii) why regimes act to reduce the rate of interactions even when no protest is observed, and (iii) that homogeneity in the structure of interactions both exacerbates the size of protests and pushes the government to extreme interventions.