This paper experimentally examines image motivation--the desire to be liked and well regarded by others--as a driver in prosocial behavior (doing good), and asks whether extrinsic monetary incentives (doing well) have a detrimental effect on prosocial behavior due to crowding out of image...

We analyze how family ties affect incentives, with focus on the strategic interaction between two mutually altruistic siblings. The siblings exert effort to produce output under uncertainty, and they may transfer output to each other. With equally altruistic siblings, their equilibrium effort is...

New ideas, products, and practices take time to diffuse, a fact that is often attributed to some form of heterogeneity among potential adopters. This paper examines three broad classes of diffusion models -- contagion, social influence, and social learning -- and shows how to incorporate...

We propose a model of cycles of conflict and distrust. Overlapping generations of agents from two groups sequentially play coordination games under incomplete information about whether the other side consists of bad types who always take bad actions. Good actions may be misperceived as bad and...

Languages differ widely in the ways they encode time. I test the hypothesis that the languages that grammatically associate the future and the present, foster future-oriented behavior. This prediction arises naturally when well-documented effects of language structure are merged with models of...

Geography and social links shape economic interactions. In industries, schools, and markets, the entire network determines outcomes. This paper analyzes a large class of games and obtains a striking result. Equilibria depend on a single network measure: the lowest eigenvalue. This paper is the...

I discuss the measurement of world poverty and inequality, with particular attention to the role of purchasing power parity (PPP) price indexes from the International Comparison Project. Global inequality increased with the latest revision of the ICP, and this reduced the global poverty line...

One lingering puzzle is why voluntary contributions to public goods decline over time in experimental and real-world settings. We show that the decline of cooperation is driven by individual preferences for imperfect conditional cooperation. Many people's desire to contribute less than others,...

Empirical work shows that a large majority of individuals get most of their information from a very small subset of the group, viz., the influencers; moreover, there exist only minor differences between the observable characteristics of the influencers and the others. We refer to these empirical...