"An institution found in many traditional societies is the extended family system (kin system), an informal system of shared rights and obligations among extended family for the purpose of mutual assistance. In predominantly non-market economies, the kin system is a valuable institution...

We show that individuals with identical preferences and abilities can self-organize into communities with starkly different civic environments. Specifically, we consider a multi-community city where community quality depends upon residents' efforts to prevent crime, improve local governance,...

Gravity models describe, and hence help predict, spatial flows of commuters, air-travelers, migrants, commodities and even messages. They are one of the oldest and most widely used of all social science models. This book presents an up-to-date, consistent and unified approach to the theory,...