Peter A. Diamond delivered his Prize Lecture on 8 December 2010 at Aula Magna, Stockholm University.

Using the Mirrlees optimal income tax model with quasi-linear preferences, the paper examines conditions for marginal tax rates to be rising at high income levels and declining in an interval containing the modal skill. It examines conditions for the marginal tax rate to be higher at a low skill level than at the high skill level with the same density--an argument only holding for skill levels above a cutoff where resources of a worker are marginally of the same value as resources of the government. Data on earnings rates are presented.

This paper explores the general-equilibrium impact of social security portfolio diversification into private securities, either through the trust fund or private accounts. The analysis depends critically on heterogeneities in saving, production, assets, and taxes. Limited diversification weakly increases interest rates, reduces the expected return on short-term investment (and the equity premium), decreases safe investment, increases risky investment, and increases a suitably weighted social welfare function. However, the effects on aggregate investment, long-term capital values, and the utility of young savers hinges on assumptions about technology. Aggregate investment and long-term asset values can move in opposite directions.

Savings and Portfolio Choice in a Two-Period Two-Asset Model by Saku Aura, Peter Diamond and John Geanakoplos. Published in volume 92, issue 4, pages 1185-1191 of American Economic Review, September 2002