This thesis presents a model of the voluntary and nonprofit sector of the economy. First it is shown that in economies in which people have different preferences for collective goods there may be residual demand for the good beyond what is provided by the government, creating a supply of potential collective good donors. Second an institutional analysis of information asymmetries in certain classes of collective and private goods shows why the voluntary sector is dominated by nonprofit organizations. Third the paper compares two otherwise identical industries, with one containing for-profit forms and the other containing nonprofit organizations, to show the different market equilibria which exist under these two institutional forms. Finally the thesis suggests an ecological approach to studying the voluntary sector as fertile ground for future development.