Professor of Economics, Harvard University, and President, National Bureau of Economic Research

^*This paper draws together conclusions of research done as part of the NBER's program of research on Social Insurance and its special research project on Capital Formation. It was presented as the Third Annual Lecture of the Geneva Association, at the Institut d'Etudes Politiques in Paris, on 15 January 1980. It was also presented as the Frank Paish Lecture at the Annual Meeting of the British Association of University Teachers in Economics. The views expressed here are personal and should not be attributed to any organization.