We consider the spread of a harmful state through a population divided into two groups. Interaction patterns capture the full spectrum of assortativity possibilities. We show that a central planner who aims for eradication optimally either divides equally the resources across groups, or...

The topic of neighbourhood-based social interactions has gained attention in the last decades in the light of urban policies that aim to deal with problems regarding social segregation and exclusion, quality of life and liveability in urban areas. Social interactions are expected to play an...

On Wikipedia, the largest online encyclopedia, editors who contribute to the same articles and exchange comments on articles’ talk pages work in collaborative manner engaging in communication about their work. Thus they can be considered as peers who are likely to influence each other. In this...

Heroes and Cowards demonstrates the role that social capital plays in people's decisions. The makeup of various companies--whether soldiers were of the same ethnicity, age, and occupation--influenced whether soldiers remained loyal or whether they deserted. Costa and Kahn discuss how the...

Many types of economic and social activities involve significant behavioral complementarities (peer effects) with neighbors in the social network. The same activities often exert externalities that cumulate in "stocks" affecting agents' welfare and incentives. For instance, smoking is subject to...