Altruism,the free rider problem and group size

This paper is a survey of recent theoretical work on the influence of group size, perceived effectiveness or noticeability of one's behavior on a group member's altruistic responses. Experiments on this problem are analyzed and evaluated, and problems for future research are outlined.This paper is a revised version of a paper originally presented at the March 1973 meetings of the Public Choice Society. In preparing this paper I have benefited from criticisms and suggestions made by a number of people and I wish to take this opportunity to thank them. Among them are John Bonin, Barry Groffman, Bob O'Gorman, Don Moon, George Reynolds and Harrison Wagner.