CLIMATE CHANGE AND OVERLAPPING GENERATIONS

This paper examines the interplay between discounting and the distribution of welfare between generations in formulating climate change response strategies. The analysis shows that one can understand Nordhaus's (1994) standard representative agent model for climate policy analysis as a reduced form of an overlapping generations model that embodies more realistic demographic assumptions. In this setting, alternative Pareto efficient allocations may be supported as competitive equilibria given appropriate sets of income transfers between generations. Numerical simulations establish that increased intergenerational transfers entail reduced monetary discount rates and increased rates of greenhouse gas emissions abatement. Short-run policy choices are highly sensitive to normative judgments concerning the relative weight attached to the welfare of future generations.     

Climate Change and the Representative Agent

The artifice of an infinitely-lived representative agent iscommonly invoked to balance the present costs and future benefitsof climate stabilization policies. Since actual economies arepopulated by overlapping generations of finite-lived persons,this approach begs important questions of welfare aggregation.This paper compares the results of representative agent andoverlapping generations models that are numerically calibratedbased on standard assumptions regarding climate--economyinteractions. Under two social choice rules -- Pareto efficiencyand classical utilitarianism -- the models generate closelysimilar simulation results. In the absence of policies toredistribute income between present and future generations,efficient rates of carbon dioxide emissions abatement rise from15 to 20% between the years 2000 and 2105. Under classicalutilitarianism, in contrast, optimal control rates rise from 48 to 79% this same period.     

An Overlapping Generations Model of Climate-Economy Interactions

A numerically calibrated overlapping generations model of climate change and the world econommy is examined in this paper. In the absence of intergenerational transfers, efficient rates of greenhouse gas emissions abatement rise from 16% in the present to 25% in the long run, while mean global temperature increases by 7.4°C relative to the preindustrial norm. A utilitarian optimum, which attaches equal weight to each generation's life-cycle utility, yields abatement rates that rise from 48% to 89%, with a long-run temperature increase of 3.4°C. A second-best utilitarian path, in which intergenerational transfers are by assumption institutionally infeasible, also supports stringent abatement measures.     

Climate-change adaptation: The role of fiscal policy

Climate change and natural disasters have important consequences on fiscal sustainability, especially for developing countries with limited financial resources and underdeveloped institutions. The paper contributes to shed light on the role of fiscal policy in climate-change adaptation, which aims at containing the economic damage of climate change. We use an overlapping generations (OLG) model for a small open economy in which adaptation reflects the extent to which public policies reduce the negative influence of climate change on the capital depreciation rate. Adaptation includes both preventive measures, i.e. investment in infrastructure, and remedial measures, i.e. post-disaster relief and reconstruction. Through model simulations we assess the costs and benefits of both remedial and preventive actions. We find that preventive intervention leads to higher GDP growth rates than either taking no action or waiting until remedial action is necessary. However, the evidence shows that, due to high costs of early adaptation and budgetary constraints, countries tend to focus on late corrective actions, also relying on international assistance. Given the expected increase in climate-related risks, a comprehensive strategy including both preventive and corrective actions would be desirable to strengthen resilience to shocks and alleviate the financial constraints, which particularly affect small countries.     

Growth,intergenerational welfare,and environmental policies in an overlapping generations economy

This paper examines the effects of the environmental tax on long‐run growth and intergenerational welfare in a discrete‐time overlapping generations (OLG ) model. We highlight that the role regarding how the environmental tax revenues are distributed between the young or old generations has important implications for the growth and welfare effects. Our results indicate that raising the environmental tax can exert different effects on the environmental utility of the existing young and old generations, implying an intergenerational welfare conflict of the environmental policy. However, if tax revenues are distributed appropriately, our numerical simulation shows that it is possible for a higher environmental tax to improve the welfare of all generations.     

Intertemporal transfers of emission quotas in climate policies

We are interested in situations in which governments are committed to some pollution abatement constraint which does not match the society's most preferred level of pollution, like in the current climate change policies undergone on behalf of the Kyoto protocol. We develop an overlapping generations model with capital and pollution in which the individuals care about the environmental quality. We show that slightly improving the intertemporal flexibility of the emission quotas by authorizing two-period backward and forward transfers allows to decentralize the whole optimal growth path at competitive equilibrium.     

Intergenerational transfers and the social discount rate

This paper investigates the relationship between intergenerational asset transfers and the choice of the discount rate for use in cost-benefit analysis in a model of a competitive overlapping generations economy constrained by a socially managed exhaustible resource. Provided that there are no distortions in capital markets and that all agents hold perfect foresight, cost-benefit techniques will result in a Pareto efficient resource allocation if the discount rate is set equal to the market rate of interest. But since the path of the interest rate depends on the level of intergenerational transfers, cost-benefit techniques do not ensure a socially desirable distribution of welfare between generations; a social optimum will result only if intergenerational transfers are properly chosen and enforced. Decentralized private altruism may result in intergenerational transfers that both present and future individuals would agree are too small if members of the present generation attach positive weight to the general welfare of future generations, not simply their personal descendants. In a world where intergenerational transfers are non-optimal, second-best policy-making may imply a constrained optimum that is inefficient. Together, these findings suggest that cost-benefit analysis is at best a partial criterion to policy formulation that should be used only in conjunction with ethical principles that define the proper distribution of welfare between present and future generations.     

Indirect taxation and the welfare effects of altruism on the optimal fiscal policy

This paper analyzes the welfare effects of altruism on the optimal fiscal policy. The existence of positive bequests links present and future generations in the economy. We show that these altruistic links provide a new role for indirect taxation (consumption and estate taxes) with important welfare implications. We use three different altruistic approaches (warm-glow, dynastic, and family) to illustrate how the presence of bequests in the budget constraint of the donee gives the government the ability to use indirect taxation to mimic lump-sum taxes and to implement the first-best outcome in the long-run. This channel is not present in economies without altruism, such as the infinite-lived consumer economy or the overlapping generations economy, where long-run welfare is suboptimal and indirect taxation is irrelevant.     

Capital Accumulation and Fiscal Policy in an OLG Model with Family Altruism

The idea of family altruism is that parents care only about their children's income and not about the use of this income made by the children. First, we establish dynamical properties which place the OLG model with family altruism halfway between the model with pure life‐cyclers ( Diamond 1965 ; American Economic Review 55, 1126–1150) and the one with dynastic altruism ( Barro 1974 ; Journal of Political Economy 82, 1095–1117). Then, we show that this concept leads to interesting fiscal policy conclusions less clear‐cut and more realistic than those obtained with the two previous standard OLG models: a pay‐as‐you‐go social security is neutral but not a public debt.     

Research Frontiers in the Economics of Climate Change

Academic and policy debates over climate change risks and policies have stimulated economic research in a variety of fields. In this article I briefly discuss eight overlapping areas of current research in which further effort is particularly warranted. These areas include decision criteria for policy; risk assessment and adaptation; uncertainty and learning; abatement cost and the innovation and diffusion of technology; and the credibility of policies and international agreements. Further analysis in these areas not only will advance academic understanding but also will provide insights of considerable importance to policymakers.     

THE WELFARE EFFECTS OF PAY-AS-YOU-GO RETIREMENT PROGRAMS: THE ROLE OF TAX AND BENEFIT TIMING

It is well known that pay-as-you-go retirement programs reduce steady-state welfare and the capital stock in dynamically efficient overlapping generation (OLG) economies. The common two-period OLG model obscures, however, the relationship between the magnitude of these effects and the ages at which taxes are paid and benefits received. Program changes that shift taxes to older workers or benefits to younger retirees have effects similar to reductions in program size, yielding steady-state welfare gains and increases in capital accumulation while imposing transition costs on current generations. This analysis has policy implications for both tax and benefit timing . ( JEL H55, E62)     

Optimal Timing of Climate Change Policy: Interaction Between Carbon Taxes and Innovation Externalities

This paper addresses the impact of endogenous technology through research and development (R&D) on the timing of climate change policy. We develop a model with a stock pollutant (carbon dioxide) and abatement technological change through R&D, and we use the model to study the interaction between carbon taxes and innovation externalities. Our analysis shows that the timing of optimal emission reduction policy strongly depends on the set of policy instruments available. When climate-specific R&D targeting instruments are available, policy has to use these to step up early innovation. When these instruments are not available, policy has to steer innovation through creating demand for emission saving technologies. That is, carbon taxes should be high compared to the Pigouvian levels when the abatement industry is developing. Finally, we calibrate the model in order to explore the magnitude of the theoretical findings within the context of climate change policy.      

Environmental Abatement and Intergenerational Distribution

This paper employs an overlapping-generations model to explore the impactof public abatement on private investment and the intergenerationaldistribution of welfare. Whereas public abatement benefits the oldestgenerations in terms of non-environmental welfare, future generations gainmost in terms of environment welfare. The overall benefits tend to besmallest for generations born at the time of the unanticipated policy shock.Public debt policy, however, can be employed to ensure that welfare gainsare distributed more equally across the various generations. Such a policyimplies that natural capital crowds-out man-made capital.     

Consumption tax and economic growth in an overlapping generations model with money holdings

This paper examines the effect of a consumption tax on economic growth using an overlapping generations (OLG) model with money holdings. We show that the neutrality of the consumption tax does not hold in the money-in-the-utility-function model, because a change in consumption taxation induces the substitution of money holdings for consumption, and the money is the net wealth within the OLG structure. An increase in the consumption tax rate lowers (raises) the growth rate under a low (high) monetary expansion rate. On the other hand, in the cash-in-advance model and the money-in-the-production-function model, the neutrality of consumption taxation holds even within the OLG structure, because in these models there is no substitution of consumption and money holdings.     

The Cost of Pollution on Longevity,Welfare and Economic Stability

This paper presents an overlapping generations model where pollution, private and public health expenditures are all determinants of longevity. Public expenditures, financed through labour taxation, provide both public health and abatement. We study the role of these three components of longevity on welfare and economic stability. At the steady state, we show that an appropriate fiscal policy may enhance welfare. However, when pollution is heavily harmful for longevity, the economy might experience aggregate instability or endogenous cycles. Nonetheless, a fiscal policy, which raises the share of public spending devoted to health, may display stabilizing virtues and rule out cycles. This allows us to recommend the design of the public policy that may comply with the dynamic and welfare objectives.     

Capital Accumulation in an Economy with Dynasties and Uncertain Lifetimes

This paper studies how the lack of an annuities market affects savings behavior and intergenerational transfers in a dynastic overlapping generations economy. I find that the answer to this question depends crucially on altruism. On the one hand, if the altruistic bequest motive is operative, then the lack of annuity markets enhances capital accumulation. On the other hand, if the altruistic bequest motive is not operative, the absence of annuity markets can either increase or decrease aggregate savings. I characterize under which conditions capital accumulation is enhanced. I also prove that an overlapping generations economy with altruism and uninsurable lifetime risk faces capital overaccumulation relative to the modified Golden Rule. The efficient allocation corresponding to the modified Golden Rule can be decentralized as a competitive equilibrium by a pay-as-you-go social security system, and this can only be done if individuals are altruistic.     

Existence and uniqueness of steady-state equilibrium in a two-sector overlapping generations model

In his seminal paper Galor [A two-sector overlapping generations-model: a global characterization of the dynamical system, Econometrica 60 (1992) 1351-1386] establishes conditions for the existence of equilibrium in the two-sector overlapping generations (OLG) model. Although appealing theoretically, these conditions are implicit and not easy to apply. This paper develops new theorems on the existence and uniqueness of steady-state equilibrium in the two-sector OLG model. We provide explicit conditions on the utility and production functions for the existence and uniqueness of equilibrium, with which one only needs to check the derivatives of the production and utility functions and their interactions, without requiring solving for the savings function and its derivatives. We present detailed steps to check the existence and uniqueness of equilibrium and provide illustrative examples.     

Optimal climate and fiscal policy in an OLG economy

This paper develops a climate–economy model to study the joint design of optimal climate and fiscal policies in economies with overlapping generations (OLGs). I demonstrate how capital taxation, if optimal, drives a wedge between the market costs of carbon (the net present value of marginal damages using the market interest rate) and the Pigouvian tax (the net present value of marginal damages using the consumption discount rate of successive OLGs). In contrast to deterministic infinitely lived representative agent models, at the optimum, the capital income tax is positive, the carbon price equals the market costs of carbon but it falls short of the Pigouvian tax when (i) preferences are not separable over consumption and leisure; and (ii) labor income taxes cannot be age-dependent. I also show that restrictions on climate change policy provide a novel rationale for positive capital income taxes.     

Self-enforcing exchange among generations: Implications for consumption and mobility

A three-generation OLG model with one-directional altruism and two-directional intra-family transfers is presented. Adults invest in their children's education and make transfers to their elderly parents. However, due to lack of altruism, adults with high earnings do not share consumption equally with their elderly parents but spend a larger share of their earnings on own consumption and on their children's education. This allows the model to be consistent with three empirical observations that are difficult to reconcile with traditional altruistic frameworks of intergenerational social interactions and mobility: (i) consumption is not perfectly shared between members of an extended family, (ii) consumption is not equally persistent over the lifecycle as across generations, and (iii) the intergenerational persistence of earnings is particularly high at the top end of the earnings distribution.     

Allocation of pollution abatement under learning by doing

This paper examines how learning by doing affects the allocation of pollution abatement between heterogeneous technologies over time. The optimal policy balances current abatement costs against reductions in future costs and infant technologies may be preferred to mature technologies despite greater initial costs. We characterize when a technological winner might emerge and we identify conditions under which optimal abatement is shared across all technologies. Pigouvian taxes can implement the first-best, but may need to be differentiated across technologies. When technical change is induced, an important role of environmental policies is to put abatement on the right technological trajectories.