Doctorandus, University Amsterdam, 1949. Honorary Dr University Amsterdam, University Freibourg.
Professor of Economics, Harvard University, 1960-1980. Member, United States President's Council Economics Advisers, 1969-1971. Henry Lee Professor of Economics, Harvard University, since 1980.
Empirical research on consumption directed at the forms of Engel curves and at dynamic phenomena. Theoretical research on that subject dealing with axiomatics and with special assumptions to improve applicability. Suggested a novel microfoundation for the production function.
Also explored the price-output behaviour of industries. In international economics demonstrated the importance of income elasticities and presented a computerised extension of the Ricardian model.