The nature of the steady state in models of optimal growth under uncertainty

Summary. We study a one-sector stochastic optimal growth model with a representative agent. Utility is logarithmic and the production function is of the Cobb-Douglas form with capital exponent . Production is affected by a multiplicative shock taking one of two values with positive probabilities p and 1-p. It is well known that for this economy, optimal paths converge to a unique steady state, which is an invariant distribution. We are concerned with properties of this distribution. By using the theory of Iterated Function Systems, we are able to characterize such a distribution in terms of singularity versus absolute continuity as parameters and p change. We establish mutual singularity of the invariant distributions as p varies between 0 and 1 whenever . More delicate is the case . Singularity with respect to Lebesgue measure also appears for values such that . For and Peres and Solomyak (1998) have shown that the distribution is a.e. absolutely continuous. Characterization of the invariant distribution in the remaining cases is still an open question. The entire analysis is summarized through a bifurcation diagram, drawn in terms of pairs .Received: 9 April 2002, Revised: 29 October 2002, JEL Classification Numbers: C61, O41.Correspondence to: Tapan MitraThis research was partially supported by CNR (Italy) under the "Short-term mobility" program and by M.U.R.S.T. (Italy) National Group on "Nonlinear Dynamics and Stochastic Models in Economics and Finance" . We are indebted to Rabi Bhattacharya for providing us with the reference to Solomyak's (1995) paper. The present version has benefitted from comments by Mukul Majumdar and two anonymous referees.     

科研开发与经济增长——兼论科研开发的溢出效应

经济划分为科研部门和非科研部门，科研开发对经济增长的作用及科研对非科研部门具有外溢效应。1999-2003年30个省市自治区的面板数据表明，科研开发对经济增长具有较大的拉动作用，同时科研开发部门对其他部门的外溢作用明显为正。     

非国有经济发展对中国经济增长质量影响机理研究——来自VEC模型的新证据

转轨以来,中国非国有经济的发展促进了经济增长的数量扩张.这是因为,经济非国有化改革作为一种制度创新,是一种增量式改革.这种改革使得体制内利益在未受影响的条件下,实现了帕雷托式的增长.然而,非国有经济的发展并没有带来中国经济增长质量的同比改善.这是因为,中国民营企业发展一般都过分强调以利润为中心,忽略环境成本,并且由于融资困难等因素导致了其技术创新能力的弱化;其次,中国引进的外资不仅在技术和管理创新的扩散效应上没能达到预期效果,而且日益增加的加工贸易通过转移定价方式使中国经济不能充分享有出口增长带来的利润贡献.     

河北省农村经济增长的消费因素影响及对策研究

当社会经济发展的主要矛盾从供给约束向需求约束转变，经济增长的主要支撑因素从供给扩张向需求拉动转变时，扩大需求成为必要。农村居民的消费水平是影响农村经济增长的重要因素，本文在介绍河北省农村居民的消费现状基础上，分析制约农村居民消费水平的因素，追而提出发展河北省农村消费市场，促进农村经济增长的对策。     

Preferences in the Future

Environmental economics has been much occupied with the discount rate, which is the value of future costs and benefits relative to present costsor benefits. But at least as important is the question of whatshould be discounted, that is, what the value of those future environmentalbenefits is to future generations. This paper analyzes the role for futurepreferences and discusses the state of knowledge. I argue that theappropriate discount rate is the market one, and that the real problemis determining future willingness-to-pay. This approach makes clearerthe connection between discounting and the valuation debate.This paper focuses on two features that have been prominent in that debate:existence value and reference dependence. I argue that thereis a vital connection between the two constructs and that this link yieldsimportant implications for future willingness-to-pay.     

Nonresponse in Contingent Valuation-reducing uncertainty in value inference

This paper focuses on problems associated with nonresponse in Contingent Valuation surveys. The results from a telephone follow-up survey show that value inference can be considerably improved by information on nonrespondents' attitudes.     

Economic Valuation of Health for Environmental Policy: Comparing Alternative Approaches. Introduction and Overview

Protecting human health is a primary goal of environmental policy and economic evaluation of health can help policy-makers judge the relative worth of alternative actions. Economists use two distinct approaches in normatively evaluating health. Whereas environmental economists use benefit-cost analysis supported by monetary valuation in terms of willingness-to-pay, health economists evaluate interventions based on cost-effectiveness or cost-utility analysis (CEA), using quality-adjusted life-years (QALY) or similar indexes. This paper provides background on the controversy about the relative merits of these approaches and introduces the remaining papers in the special issue. These papers (with one exception) were presented at a conference sponsored by the Department of Economics at the University of Central Florida with support from the US Environmental Protection Agency. Although CEA might not lead to substantially different implications for environmental policy than benefit-cost analysis, and QALY may provide a benefit transfer tool to fill gaps in the morbidity valuation literature, the papers in this issue raise serious concerns about the suitability of QALY-based CEA for environmental regulatory analysis. QALY does not in general appropriately represent individual preferences for health and CEA is neither independent of income distribution nor adequate to assess efficiency.     

The Productivity of US States since 1880

This study uses state-level variation in labor productivity levels at twenty-year intervals between 1880 and 1980 to examine the relative importance of institutional and geographical influences in explaining observed and persistent differences in standards of living over time and across regions. Focusing on fundamental rather than proximate influences, we find that both institutional characteristics and some physical geography characteristics account for a high proportion of the differences in state productivity levels: states with navigable waterways, a large minerals endowment, and no slaves in 1860, on average, had higher labor productivity levels throughout the sample period. However, we find little support for two other influences that have previously received attention—climate and latitude.     

Quantitative growth effects of subsidies in a search theoretic R&D model

Should government subsidize R&D and does it matter how these subsidies are allocated? We examine these questions in a dynamic model where R&D is described as sequential sampling from a distribution of new ideas. Successful discoveries affect future available resources and incentives for further R&D. Consequently, there may be under-investment in R&D. We study the effect of government interventions aimed at fostering growth through R&D. Calibrating the model with aggregate data from the Israeli business sector allows us to quantitatively compare two forms of support resembling those actually used to encourage R&D in the Israeli business sector: (i) an unrestricted subsidy that may be used at the recipients' discretion to finance R&D or other investments, (ii) a subsidy earmarked by the government for R&D activities only. While there is no theoretical way to determine which of the two subsidies will have a greater impact on search for new ideas and growth, we find that in the calibrated economy both subsidies have a significant but similar impact on the economy's output and TFP growth rates. Accordingly, in the case of the Israeli business sector, the incentives to conduct R&D were sufficiently strong, and no R&D-specific encouragement was needed. However, a sensitivity analysis reveals that for economies characterized by other parameter values this result may not be true. Correspondence to: B. Bental     

生态经济学基本问题研究

如何审视生态系统、环境系统与经济系统之间的相互关系,关系到对生态经济学基本问题的科学理解,关系到如何运用科学发展观建设和谐社会、实现经济社会持续发展。本文以此为前提,深入研究生态经济学的基本问题,对生态价值、环境价值、经济价值层次的升级,逻辑上的升华及其内在联系进行了探讨。