This paper considers a dynamic model of the evolution of open source software projects, focusing on the evolution of quality, contributing programmers, and users who contribute customer support to other users. Programmers who have used open source software are motivated by reciprocal altruism to...

Transplants of donated stem cells save the lives of many patients with blood diseases. Donation is somewhat painful, but rarely has lasting adverse effects. Patients can accept transplants only from donors with compatible immune systems. Those lacking a sibling match must seek donations from the...

Transplants of donated stem cells save the lives of many patients with blood diseases. Donation is somewhat painful, but rarely has lasting adverse effects. Patients can accept transplants only from donors with compatible immune systems. Those lacking a sibling match must seek donations from the...

This paper surveys the literature on group selection. I describe the early contributions and the group selection controversy. I also describe the main approaches to group selection in the recent literature; fixation, assortative group formation, and reproductive externalities. -- Altruism ; spite...

The literature suggests that the household invests in the human capital of a child member not only for altruistic reasons but also as insurance against future income shocks. Hence, the allocation of the child's time between school and work is a function of the risk preference of the household...

I study attitudes towards risk taking in cases where a person relates to others positively, namely altruistically. This study is needed because it is unclear how altruism influences the inclination of an altruistic person to take risks. Will this person's risk-taking behavior differ if the...

I study attitudes towards risk taking in cases where a person relates to others positively, namely altruistically. This study is needed because it is unclear how altruism influences the inclination of an altruistic person to take risks. Will this person's risk-taking behavior differ if the...

There are currently debates both about the ability to measure the value of moral sentiments and the nature of benefit-cost analysis. Moral sentiments can be reasonably measured in many situations and their consideration can improve benefit-cost analysis in any case. This argument is presented by...

We conduct field experiments in a large real-world social network to examine why decision-makers treat their friends more generously than strangers. Subjects are asked to divide a surplus between themselves and named partners at varying social distances, but only one of these decisions is...