We calculate the equilibrium fraction of cooperators in a population in which payoffs accrue from playing a single-shot prisoner's dilemma game. Individuals who are hardwired as cooperators or defectors are randomly matched into pairs, and cooperators are able to perfectly find out the type of a...

Quite often established migrants offer assistance and support that facilitate the arrival of new migrants. Why would migrants want other migrants to join them - so much so as to be willing to pay for them to come? We suggest a rationale. Our modeling framework is capable of explaining several...