Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
We develop a model in which connections between individuals serve as social collateral to enforce informal insurance payments. We show that: (i) The degree of insurance is governed by the expansiveness of the network, measured with the per capita number of connections that groups have with the rest of the community. "Two-dimensional" networks?like real-world networks in Peruvian villages?are sufficiently expansive to allow very good risk-sharing. (ii) In second- best