On optimality in intergenerational risk sharing

Summary. This paper defines and studies optimality in a dynamic stochastic economy with finitely lived agents, and investigates the optimality properties of an equilibrium with or without sequentially complete markets. Various Pareto optimality concepts are considered, including interim and ex ante optimality. We show that, at an equilibrium with a productive asset (land) and sequentially complete markets, the intervention of a government may be justified, but only to improve risk sharing between generations. If markets are incomplete, constrained interim optimality is investigated in two-period lived OLG economies. We extend the optimality properties of an equilibrium with land and give conditions under which introducing a pay-as-you-go system at an equilibrium would not lead to any Pareto improvement. Received: October 5, 1998; revised version: April 3, 2001     

Government Deficit, Public Investment, and Public Capital in the Transition to an Aging Japan

This paper examines the effects of government deficits, public investment, and public capital on welfare in the transition to an aging Japan by applying a simulated general equilibrium growth model. One of the main results of this paper is that targeting only high economic growth would mislead us as to economic policies, and that a policy to reduce future government deficits is most preferable for almost all generations, even though a cut in future deficits must be followed by a decrease in public investment, thus a decrease in public capital in the future. J. Japan. Int. Econ., December 2002, 16(4), pp. 462–491. Faculty of Economics, Shiga University, Japan; and Management School, Imperial College, United Kingdom. © 2002 Elsevier Science (USA).Journal of Economic Literature Classification Numbers: H55, H54, H62, C68, J10.     

Overlapping Generations or Infinitely-Lived Agents: Intergenerational Altruism and the Economics of Global Warming

Do we need an overlapping generations model for the economics of global warming? To answer this question, an infinitely-lived agent (ILA) approach and an overlapping generations (OLG) model are contrasted. ILA and OLG can be viewed as polar representations of intergenerational altruism. With ILA an immortal agent acts through his investment/savings decisions as trustee on the behalf of the future generations. With OLG, agents need not behave altruistic. They simply save during working years and dissave completely during retirement. Nevertheless, ILA and OLG must not differ in their implication for greenhouse policy. Greenhouse gas abatement is a straightforward alternative to physical capital formation and, even without altruism, each age cohort has an incentive to provide current abatement in order to reduce future damages attributable to climate change. Indeed, under reasonable assumptions and parameter values, our simulations reveal such an invariance result. Provided carbon taxes are the only policy tool and tax revenues are recycled through socially mandated rules, projections of economic growth, climate change and energy consumption are only insignificantly affected by the choice of approach.     

Perpetual youth and endogenous labor supply: A problem and a possible solution

In the “perpetual youth” overlapping-generations model of Blanchard and Yaari, if leisure is a “normal” good then some agents will have negative labor supply. We suggest a solution to this problem by using a modified version of Greenwood, Hercowitz and Huffman’s utility function. The modification incorporates real money balances, so that the model may be used to analyze monetary as well as fiscal policy. In a Walrasian version of the economy, we show that increased government debt and increased government spending raise the interest rate and lower output, while an open-market operation to increase the money supply lowers the interest rate and raises output.     

Unemployment dynamics in an OLG economy with public pensions

Pension benefits in old age establish a disincentive to save in youth, thereby yielding lower levels of capital stock and the wage rate. As a result, the trade union has an incentive to change the composition of its two targets: employment and the wage rate. This paper develops a model that includes employment effects of public pensions via capital accumulation and union wage setting. Within this framework, we consider how contribution rates to the pension system influence the level and time path of the unemployment rate. It is demonstrated that (1) a higher contribution rate results in a lower unemployment rate, and (2) the economy with a high (low) contribution rate experiences monotone convergence towards (oscillatory convergence towards or a period-2 cycle around) the steady state. The author would like to thank an anonymous referee, Kazutoshi Miyazawa, and seminar participants at Osaka University for their useful comments and suggestions, and Masako Ikefuji and Hiroaki Yamagami for their research assistance. Financial support from the Japan Society for the Promotion of Science (JSPS) through a Grant-in-Aid for Young Scientists (B) (No.17730131), the Asahi Glass Foundation, the Japan Economic Research Foundation and the 21st Century COE Program (Osaka University) is gratefully acknowledged. All remaining errors are mine.     

Environmental tax policy in a model of growth cycles

Summary. The purpose of this paper is to consider environmental taxation which would control emissions of firms in a model of growth cycles. In the model presented below, the economy may experience two phases of growth and environmental quality: “the no-innovation growth regime” and “the innovation-led growth regime”. Aggregate capital and environmental quality remain constant in the no-innovation growth regime, while they perpetually increase in the innovation-led growth regime. The paper shows that the tax plays a key role in determining whether the economy stably converges to one of the two regimes or fluctuates permanently between them. It also shows that there is a critical level of the tax and that the economy obtains higher growth rates of capital and environmental quality by raising (or reducing) the tax if the initial tax is below (or above) the critical level. Received: April 2, 2001; revised version: March 21, 2002 RID="*" ID="*" This research reported here was conducted within the research project “Project on Intergenerational Equity” at Institute of Economic Research, Hitotsubashi University. I am deeply grateful to an anonymous referee for his or her insightful comments, which greatly improved the paper. I also thank Hiroshi Honda, Yasuo Maeda, Yuji Nakayama, and participants in workshops at Hitotsubashi University, Kyoto University, Nagoya University, Osaka University, University of Tsukuba, Yokohama National University, and University of Tokyo for their valuable comments and suggestions. Any remaining errors are mine.     

Stone–Geary preferences in overlapping generations economies under pure exchange: A note

We incorporate Stone–Geary preferences into an overlapping generations economy under pure exchange, and explore stability, indeterminacy, and cycles with positive levels of saving and nonnegative public debt. A stable nontrivial steady state exists for parameter values, for which there does not exist equilibrium in the model with purely logarithmic utility function. We also show the possibility of a period-doubling bifurcation (a two-cycle).     

Learning of cycles and sunspot equilibria by Genetic Algorithms

We analyze the learning behaviour of a Simple Genetic Algorithm in an overlapping generations model with one consumption good and fiat money. It is shown by simulations, that in cases where periodic equilibria exist the equilibrium of period two is learned by a Genetic Algorithm and not the monetary steady state. We further show that proper coding leads to convergence of the GA towards the sunspot equilibrium. If individuals who believe in the impact of sunspots are brought together with individuals who ignore the sunspots, the sunspot believes will in most cases drive the other individuals out of the population.     

持续发展中代际财富转移简单模型

代际均衡发展是持续发展论的主要内容之一，其中代际财富转移和贴现率应用是其核心内容。本文探讨了一个代际财富转移的简单模型，并采用人们熟悉的柯布──道格拉斯函数形式表达。模型的敏感因素为利息率、工资和自然资源价格，并且是由代际间的跨代收入分配决定的。贴现率等于同期利息率，其水平是变动的。     

Overlapping Generations and Environmental Policy： An Introduction

A small but growing body of literature uses overlapping generations （OLG） models to study environmental policy for long-lived problems such as climate change. An OLG model, unlike the infinitely lived representative agent model, dis- tinguishes between impatience with respect to one＇s own future utility, and attitudes toward successors＇ utility. I discuss the problem of time inconsistency, the role of Markov perfection, and show that a class of OLG models can be studied using me- thods developed to analyze models of non-constant discounting. An example illu- strates the techniques and determines the conditions under which, in equilibrium, there is under-investment or over-investment in natural capital.