Attempts to develop a methodology for answering some important but usually ignored questions about the potential supply of applicants for public employment programs. The practical methodology which is outlined can be used to estimate the size and composition of the supply population for various public employment programs, and to help illuminate some of the issues associated with public employment. For illustrative purposes, some of the discussion references the 1967 Survey of Economic Opportunity, a dataset that incorporates the information necessary to implement the methodology. Using the methods presented in this paper and the 1967 Survey of Economic Opportunity, estimates can be made of how many persons would have preferred employment in a given public employment program in 1966, had that option been available to them. 48 pp.