How to invest over the life cycle: Insights from theory

We analyse the state of the art in the field of life cycle portfolio choice, a recent strand of the literature on intertemporal portfolio selection. Life cycle models are designed to identify optimal savings and portfolio policies over the lifetime of investors. They can help to improve pension schemes by showing how these could be specifically tailored to the individual employee’s circumstances to overcome the ‘one-size-fits-all’ philosophy still prevailing in parts of the mandatory retirement savings system. To facilitate comparison, we first describe set-up, solution method and characteristic results for a basic model and then derive a general framework to classify existing contributions. We highlight the models’ strengths and weaknesses and assess their ability to resolve existing portfolio puzzles. Lessons from the literature are summarized and promising areas for further research identified. JEL classifications G11, D14, D91, H55     

The Helios strategy: An heretical view of the potential role of solar energy in the future of a small planet

Over the next hundred years there must be a worldwide transition from reliance on fossil fuels to the use of some combination of long-term and abundant primary sources for the production of heat, electricity, and synthetic fuels. The rate at which such options can be developed and employed, as well as the maximum rate at which they can provide energy at a sustained rate, will place important constraints on the rate and limits to growth of other human activities. It is generally argued that only the fission option, in the form of the fast-breeder and high-temperature reactors, can provide the energy required for a livable world, particularly if this means a world of 10 billion people living at the present energy level of Western Europe. However, a careful examination indicates that the use of solar energy, through a menu of technological options, can provide the needs of a world at this scale of energy use, and that this can be accomplished within the constraints of land availability and requirements for energy, materials, and labor. No scientific breakthroughs are required, although a number of these would be helpful, but very substantial engineering advances are required, and the transition of such a world-wide system would take no less than a century. However, the feasibility of such large-scale use of solar energy will substantially alter those aspects of the “limits to growth” discussions in which future growth strategies are constrained by available and acceptable energy alternatives. This paper outlines a global solar-energy system considered feasible for more than 10 billion people living at 5 kW per capita.     

A theory of sequential reciprocity

Many experimental studies indicate that people are motivated by reciprocity. Rabin [Amer. Econ. Rev. 83 (1993) 1281] develops techniques for incorporating such concerns into game theory and economics. His theory is developed for normal form games, and he abstracts from information about the sequential structure of a strategic situation. We develop a theory of reciprocity for extensive games in which the sequential structure of a strategic situation is made explicit, and propose a new solution concept—sequential reciprocity equilibrium—for which we prove an equilibrium existence result. The model is applied in several examples, and it is shown that it captures very well the intuitive meaning of reciprocity as well as certain qualitative features of experimental evidence.     

Persistence of Shocks to Output in Austria and Theories of Economic Growth

The paper analyzes the degree of output persistence in GDP in order toempirically discriminate between the Solow growth model, the perfect competition endogenous growth model and the imperfect competition endogenous growth model for the case of Austria. Wefind that a shock in the growth rate of output induces a permanent and larger effect on the level of GDP. This leads us to refute the Solow growth model and the perfect competition model of endogenous growth.We may not reject the imperfect competition growth model.     

Assessing Preference Change on the US Supreme Court

The foundation upon which accounts of policy-motivated behaviorof Supreme Court justices are built consists of assumptionsabout the policy preferences of the justices. To date, mostscholars have assumed that the policy positions of Supreme Courtjustices remain consistent throughout the course of their careersand most measures of judicial ideology—such as Segal andCover scores—are time invariant. On its face, this assumptionis reasonable; Supreme Court justices serve with life tenureand are typically appointed after serving in other politicalor judicial roles. However, it is also possible that the worldviews,and thus the policy positions, of justices evolve through thecourse of their careers. In this article we use a Bayesian dynamicideal point model to investigate preference change on the USSupreme Court. The model allows for justices' ideal points tochange over time in a smooth fashion. We focus our attentionon the 16 justices who served for 10 or more terms and completedtheir service between the 1937 and 2003 terms. The results arestriking—14 of these 16 justices exhibit significant preferencechange. This has profound implications for the use of time-invariantpreference measures in applied work.     

Uncertainty and sustainability in the management of rangelands

We analyze a dynamic and stochastic ecological-economic model of grazing management in semi-arid rangelands. The ecosystem is driven by stochastic precipitation. A risk averse farmer chooses a grazing management strategy under uncertainty such as to maximize expected utility from farming income. Grazing management strategies are rules about which share of the rangeland is given rest depending on the actual rainfall in that year. In a first step we determine a myopic farmer's optimal grazing management strategy and show that a risk averse farmer chooses a strategy such as to obtain insurance from the ecosystem: the optimal strategy reduces income variability, but yields less mean income than possible. In a second step we analyze the long-run ecological and economic impact of different strategies. We conclude that a myopic farmer, if he is sufficiently risk averse, will choose a sustainable grazing management strategy, even if he does not take into account long-term ecological and economic benefits of conservative strategies.     

Uncertain lifetimes and the welfare enhancing properties of annuity markets and social security

This paper explores the implications of social security programs and annuity markets through which agents, who are characterized by different distributions of length of lifetime, share death-related risks. When annuity markets operate, a non-discriminatory social security program affects only the intragenerational allocation of resources. In the absence of private information regarding individual survival probabilities, such a program will lead to a non-optimal intragenerational allocation of resources. However, the presence of adverse selection considerations gives rise to a Pareto improving role for a mandatory non-discriminatory social security program.     

Gold,liquidity and secured loans in a multistage economy Part I: Gold as money

This work relates to Department of the Navy Contract N00014-86-K0220 issued by the Office of Naval Research under Contract Authority NR 047-006. However, the content does not necessarily reflect the position or the policy of the Department of the Navy or the Government, and no official endorsement should be inferred. Revised with support of NSF contract SES-8812051.The United States Government has at least a royalty-free, non-exclusive and irrevocable license throughout the world for Government purposes to publish, translate, reproduce, deliver, perform, dispose of, and to authorize others so to do, all or any portion of this work.     

The recent failure of U.S. monetary policy

Summary The very slow growth of the broad money supply has been a primary source of U.S. economic weakness in 1990 through 1992. The velocity link between M2 and the subsequent level of nominal GDP has not declined. But changes in bank reserves brought about by open market operations have had much less effect onM2 than the Fed anticipated for two reasons: (1) reserve requirements now apply to only a small fraction of totalM2; and (2) the new bank capital requirements limit some banks ability to lend. The Federal Reserve failed to appreciate the importance of these conditions and misjudged the strength of the monetary policy stimulus that it was providing.Professor of Economics, Harvard University, and President of the National Bureau of Economic Research.Sixth Tinbergen Lecture delivered on October 2, 1992, in The Hague for the Royal Netherlands Economic Association.