the greenhouse effect damages costs and abatement the buildup of so called greenhouse gases in the atmosphere co2 in particular appears to be having an adverse impact on the global climate this paper briefly reviews current expectations with regard to physical and biological effects their potential costs to society and likely costs of abatement for a worst case scenario it is impossible to assess in economic terms the full range of possible non linear synergistic effects in the most favorable although not necessarily likely case of slow paced climate change however it seems likely that the impacts are within the affordable range at least in the industrialized countries of the world in the third world the notion of affordability is of doubtful relevance making the problem of quantitative evaluation almost impossible we tentatively assess the lower limit of quantifiable climate induced damages at 30 to 35 per ton of co2 equivalent worldwide with the major damages being concentrated in regions most adversely affected by sea level rise the non quantifiable environmental damages are also significant and should by no means be disregarded the costs and benefits of 1 reducing cfc use and 2 reducing fossil fuel consumption as a means of abatement are considered in some detail this strategy has remarkably high indirect benefits in terms of reduced air pollution damage and even direct cost savings to consumers the indirect benefits of reduced air pollution and its associated health and environmental effects from fossil fuel combustion in the industrialized countries range from 20 to 60 per ton of co2 eliminated in addition there is good evidence that modest e g 25 reductions in co2 emissions may be achievable by the u s and by implication for other countries by a combination of increased energy efficiency and restructuring that would permit simultaneous direct economic benefits savings to energy consumers of the order of 50 per ton of co2 saved a higher level of overall emissions reduction possibly approaching 50 could probably be achieved at little or not net cost by taking advantage of these savings we suggest the use of taxes on fossil fuel extraction or a carbon tax as a reasonable way of inducing the structural changes that would be required to achieve significant reduction in energy use and co2 emissions to minimize the economic burden and create a political constituency in support of the approach we suggest the substitution of resource based taxes in general for other types of taxes on labor income real estate or trade that are now the main sources of government revenue while it is conceded that it would be difficult to calculate the optimal tax on extractive resources we do not think this is a necessary prerequisite to policy making in fact we note that the existing tax system has never been optimized according to theoretical principles and is far from optimal by any reasonable criteria

are optimal emissions really optimal four critical issues for economists in the greenhouse although the greenhouse effect is by many considered as one of the most serious environmental problems several economic studies of the greenhouse effect most notably nordhaus s dice model suggest that it is optimal to allow the emissions of greenhouse gases ghg to increase by a factor of three over the next century other studies have found that substantial reductions can be justified on economic grounds this paper explores into the reasons for these differences and identifies four partly overlapping crucial issues that have to be dealt with when analysing the economics of the greenhouse effect low probability but catastrophic events cost evaluation methods the choice of discount rate the choice of decision criterion the paper shows that i these aspects are crucial for the policy conclusions drawn from models of the economics of climate change and that ii ethical choices have to be made for each of these issues this fact needs wider recognition since economics is very often perceived as a value neutral tool that can be used to provide policy makers with optimal policies

efficiency wages and the business cycle puzzle abstract the main thrust of this work is to open the real business cycle rbc methodology to non walrasian considerations and reciprocally to submit some non walrasian models to the discipline of the rbc approach in doing so we provide a first rbc model with involuntary unemployment and a suboptimal equilibrium path we also demonstrate the promise and difficulty of resolving the business cycle puzzle by appealing to quantity rationing in the labor market

valuing the impact of co2 emissions valuing the impacts of co2 emissions to the atmosphere has been widely debated with various studies suggesting very different costs when expressed in units of dollar per tonne of carbon emitted there are many complex issues involved and it is often difficult to determine the reasons for the wide range of costs proposed in this paper models based on two very different approaches the page and intera models are considered by applying these models to calculating the marginal impact of co2 emissions it is shown that what appear initially to be divergent estimates can be reconciled this process illustrates some of the key issues in this area and a perspective is provided on which marginal costs are appropriate for different policy decisions

taxing fossil fuels under speculative storage long term environmental consequences of taxing fossil fuel usage have been extensively studied in the literature however these taxes may also impose several short run macroeconomic policy challenges the nature of which remains underexplored this paper investigates the mechanisms through which environmental taxes on fossil fuel usage can affect the main macroeconomic variables in the short run we concentrate on a particular mechanism speculative storage formulating and using a dynamic stochastic general equilibrium dsge model calibrated for the united states with an explicit storage facility and nominal rigidities we show that in designing environmental tax policies it is crucial to account for the fact that fossil fuel prices are subject to speculation the existence of forward looking speculators in the model improves the effectiveness of tax policies in reducing fossil fuel usage improved policy effectiveness however is costly it drives inflation and interest rates up while impeding output based on this tradeoff we seek an answer to the question how monetary policy should interact with environmental tax policies in our dsge model of fossil fuel storage we show that in an environment with no speculative storers monetary policy should respond to output along with cpi inflation in order to minimize the welfare losses brought by taxes however when the storage facility is activated responding to output in the monetary policy rule becomes less desirable

the damage costs of climate change a note on tangibles and intangibles applied to dice economic cost benefit analysis of the costs of greenhouse gas emission abatement and climate change often points towards limited abatement this note elucidates one reason why this result is obtained the way in which the intangible damages are treated and the utility function is specified on the basis of the dice model it is shown that by putting the intangible damages directly into the utility function and by assuming them to grow with per capita income the optimal reduction increases and in the second case more than triples compared to nordhaus s original results

learning by doing vs learning about match quality can we tell them apart understanding the accumulation of match specific capital is crucial in shedding light on the reasons for the prevalence of long term employ ment relationships and on the welfare consequences of turnover in the labor market one of the most important source of match specific capital is human capital acquired through match specific learning such learn ing can take on two distinct forms in the first case workers accumulate match specific human capital through learning by doing in the second case a worker and a firm in an employment relationship learn about the quality of the match over time thereby acquiring valuable information i construct a structural model that embeds these two learning explana tions i show that it is possible to distinguish the two explanations given turnover data on employing firms coupled with data on workers such data now exist in the form of matched employer employee data sets i use a matched french data set to estimate the structural model using the efficient method of moments a simulation based estimation method i find that while learning by doing could be present in the first few months of an employment relationship learning about match quality dominates at tenures above half a year this finding has important consequences for economists understanding of the sources of match specific capital and for the desirability of policies that alter the incentives for turnover for workers of different tenure

estimates of the economic effects of sea level rise regional estimates of direct cost dc are commonly used to measure the economic damages of sea level rise such estimates suffer from three limitations i values of threatened endowments are not well known ii loss of endowments does not affect consumer prices and iii international trade is disregarded results in this paper indicate that these limitations can significantly affect economic assessments of sea level rise current uncertainty regarding endowment values as reflected in two alternative data sets for example leads to a 17 percent difference in coastal protec tion a 36 percent difference in the amount of land protected and a 36 percent difference in dc globally also global losses in equivalent variation ev a welfare measure that accounts for price changes are 13 percent higher than dc estimates regional ev losses may be up to 10 percent lower than regional dc however because international trade tends to redistribute losses from regions with relatively high damages to regions with relatively low damages

equitable cost benefit analysis of climate change policies the literature of welfare maximising greenhouse gas emission reduction strategies pays remarkably little attention to equity this paper introduces three ways to consider efficiency and equity simultaneously the first method inspired by kant and rawls maximises net present welfare without international cooperation as if all regions share the fate of the region affected worst by climate change optimal emission abatement varies greatly depending on the spatial and temporal resolution that is the grid at which maximum impact is defined the second method is inspired by varian s no envy emissions are reduced so as to equalise total costs and benefits of climate change over all countries of the world and over all time periods emission reductions are substantial this method approximately preserves the inequities that would occur in a world without climate change the third method uses non linear aggregations of welfare the utilitarian default is linear in a cooperative setting this method cannot distinguish between sources of inequity the higher the aversion to inequity the higher optimal greenhouse gas emission reduction

second best policies for congestion externalities abstract this is the third in a series of three articles on the topic of congestion externalities we use an urban general equilibrium model to test the efficiency of several second best policies for congestion externalities the most efficient second best policy is a program of land use controls the program generates a welfare gain of 3 38 per household per week a unit tax on commuting is a less efficient policy with a welfare gain of 1 15

carbon markets and technological innovation this paper examines the effects of firm level innovation in carbon abatement technologies on optimal cap and trade schemes with and without price controls we characterize optimal cap and trade regulation with a price cap and a price floor and compare it to the special cases of pure taxation and a simple emissions cap innovation shifts the tradeoff between price and quantity based instruments towards quantitybased emissions trading schemes more specifically an increase in innovation effectiveness lowers the optimal emissions cap and leads to relaxed price controls unless the slope of the marginal environmental damage curve is small because of the decrease in the emissions cap innovation in abatement technologies can lead to a higher expected carbon price so as to provide sufficient incentives for private r d investments the expected carbon price decreases once innovative technologies are widely used

equilibrium matching and termination in an equilibrium model of the labor market with moral hazard jobs are dynamic contracts job separations are terminations of optimal dynamic contracts transitions from unemployment to new jobs are modeled as a process of random matching and nash bargaining non employed workers make consumption and saving decisions as in a standard growth model as well as whether or not to participate in the labor market the stationary equilibrium is characterized the model is then calibrated to the u s labor market to study quantitatively the worker flows and distributions the compensation dynamics and the effects of ui system

competitive equilibrium with search frictions a general equilibrium approach abstract when the trading process is characterized by search frictions traders may be rationed so markets need not clear we build a general equilibrium model with transferable utility where the uncertainty arising from rationing is incorporated in the definition of a commodity in the spirit of the arrow debreu theory prices of commodities then depend not only on their physical characteristics but also on the probability that their trade is rationed the standard definition of competitive equilibrium is extended by replacing the market clearing condition with an exogenous matching function which describes a trading technology that is not frictionless as is typical in search models the matching function relates the rationing probabilities of buyers and sellers to the ratio of buyers to sellers in the market when search frictions vanish our model is equivalent to the continuous assignment model of gretsky et al 20 we adapt their approach which uses linear programming techniques and duality theory to show that a competitive equilibrium exists and is constrained efficient in our environment our competitive equilibrium notion is equivalent to that of directed or competitive search the strength of our formulation and the linear programming approach is that they allow us to generalize the constrained efficiency and existence results in the directed search literature to a much broader class of economies our framework also opens the door to the use of existing algorithms for computing equilibria and taking these models to the data

urban economic theory land use and city size this book examines the economic reasons why people choose to live where they live and develops through analysis of the bid rent function a unified theory of urban land use and city size the first part of the book explicates the basic theory of urban land use and optimal city size residential location behavior of households is examined in a microeconomic framework and equilibrium and optimal patterns of residential land use are discussed the corresponding equilibrium and optimal city sizes are studied in a variety of contexts part two extends the classical theories of von thunen and alonso with the addition of externality factors such as local public goods crowding and congestion and racial prejudice the rigorous mathematical approach and theoretical treatment of the material make urban economic theory of interest to researchers in urban economics location theory urban geography and urban planning

external costs of energy do the answers match the questions looking back at 10 years of externe abstract while the claim for getting prices right is quite popular in conceptual policy papers the implementation of appropriate internalisation strategies is still hampered by a lack of reliable external cost data great expectations were set into the externe project a major research programme launched by the european commission at the beginning of the 1990s to provide a scientific basis for the quantification of energy related externalities and to give guidance supporting the design of internalisation measures after more than a decade of research the externe label became a well recognised standard source for external cost data looking back into the externe history the paper pursues how emerging new scientific insights and changing background assumptions affected external cost estimates and related recommendations to policy over time based on externe results the usefulness and inherent limitations of external cost estimates for impact categories like climate change or nuclear waste disposal is discussed the paper also gives examples on how external costs in spite of remaining uncertainties are successfully used to support environmental policy

weight factors in cost benefit analysis of climate change equity considerations may justify the use of weight factors when estimating the costs of climate change this paper reviews different weight factors that have been used in the climate economics literature based on a simple model it is shown that although the different weight factors imply substantially different cost damage estimates they actually yield the same optimal emission reductions this paradox is explained by the fact that some of the approaches require that also the abatement costs are weighted and this offsets the effect of the diverging cost damage estimates the model is then used to analyse the importance weighting may have on the overall cost benefit analysis at present when most of the global emissions of fossil co2 originate from the industrialised countries the global optimal emissions are considerably lower if costs are weighted however the more the emissions in developing countries grow the less important becomes the introduction of weight factors in cost benefit analysis of climate change for the global emission reductions in the model developed here on a regional level the introduction of weight factors continues to play an important role implying substantially lower emissions in the rich region and slightly higher in the poor

a theory of disagreement in repeated games with bargaining this paper proposes a new approach to equilibrium selection in repeated games with transfers supposing that in each period the players bargain over how to play although the bargaining phase is cheap talk following a generalized alternating offer protocol sharp predictions arise from three axioms two axioms allow the players to meaningfully discuss whether to deviate from their plan the third embodies a theory of disagreement that play under disagreement should not vary with the manner in which bargaining broke down equilibria that satisfy these axioms exist for all discount factors and are simple to construct all equilibria generate the same welfare optimal play under agreement generally requires suboptimal play under disagreement whether patient players attain efficiency depends on both the stage game and the bargaining protocol the theory extends naturally to games with imperfect public monitoring and heterogeneous discount factors and yields new insights into classic relational contracting questions

competitive search equilibrium in this paper i construct an equilibrium for markets with frictions which is competitive in the sense that all agents are price takers and maximize utility subject to a set of market parameters i show that the equilibrium allocation is socially optimal i also show how the competitive search equilibrium can be achieved if employers with vacancies can advertise publicly the wages they pay

dynamic contracts with worker mobility via directed on the job search this article proposes a model with dynamic incentive contracts and on the job search in a frictional labor market the optimal long term contract exhibits an increasing wage tenure profile with increasing wages worker effort also increases with tenure these two features imply that the probabilities of both voluntary and involuntary job separation decrease with both job tenure and the duration of employment given these results workers experience differing labor market transitions between employment unemployment and across different employers and the equilibrium generates endogenous heterogeneity among ex ante homogeneous workers abstract from author

the aggregation of climate change damages a welfare theoretic approach the economic value of environmental goods is commonly determined using the concepts of willingness to pay wtp or willingness to accept wta however the wtp wta observed in different countries or between individuals will differ according to socio economic characteristics in particular income this notion of differentiated values for otherwise identical goods say a given reduction in mortality risk has been criticized as unethical most recently in the context of the social cost chapter of the ipcc second assessment report these critics argue that being a function of income wtp wta estimates reflect the unfairness in the current income distribution and for equity reasons uniform per unit values should therefore be applied across individuals and countries this paper analyses the role of equity in the aggregation of climate change damage estimates using basic tools of welfare economics it shows one way of how wtp wta estimates can be corrected in aggregation if the underlying income distribution is considered unfair it proposes that in the aggregation process individual estimates be weighted with an equity factor derived from the social welfare and utility functions equity weighting can significantly increase aggregate global damage figures although some specifications of weighting functions also imply reduced estimates the paper also shows that while the postulate of uniform per unit values is compatible with a wide range of reasonable utility and welfare specifications there are also cases where the common value notion is not compatible with defensible welfare concepts

climate change and optimal energy technology r d policy public policy response to global climate change presents a classic problem of decision making under uncertainty theoretical work has shown that explicitly accounting for uncertainty and learning in climate change can have a large impact on optimal policy especially technology policy however theory also shows that the specific impacts of uncertainty are ambiguous in this paper we provide a framework that combines economics and decision analysis to implement probabilistic data on energy technology research and development r d policy in response to global climate change we find that given a budget constraint the composition of the optimal r d portfolio is highly diversified and robust to risk in climate damages the overall optimal investment into technical change however does depend in a non monotonic way on the risk in climate damages finally we show that in order to properly value r d abatement must be included as a recourse decision

rethinking the costs related to global warming a survey of the issues one approach to the economic analysis of global warming seeks to balance the costs of damage from or adaptation to it with the costs of mitigating it the costs of adaptation and damage have been estimated using techniques of environmental evaluation but are subject to a wide margin of uncertainty the costs of mitigation principally by reducing the emissions of co2 have been estimated using different kinds of economic models some of the results of which have suggested that very little abatement of carbon emissions is justified before the costs of abatement exceed the benefits of it in terms of foregone damage and adaptation costs the paper analyses the extent to which this conclusion is a function of the modelling assumptions and techniques used rather than likely practical outcomes with regard to the models treatment of unemployed resources revenue recycling prior distortions in the economy due to the tax system and possible dynamic effects from the introduction of a carbon energy tax it concludes that with different and arguably more appropriate treatment of the above issues especially when the secondary benefits of reducing co2 emissions are also taken into account it is not clear that even substantial reductions in the use of fossil fuels will incur net costs especially if there is the prospect of even moderate costs from global warming

the social cost of carbon and its policy implications the shadow price or social cost of carbon is an important indicator of the global incremental damage done by emitting greenhouse gases today cost benefit analysis would set the optimal amount of greenhouse gas emission reduction at the point where this social cost just equals the incremental cost of controlling emissions the higher the value for the social cost of carbon the more control is warranted this comparison assumes that cost benefit analysis is the correct way of determining climate change policy and many believe this is not the case because of the very long term irreversible and potentially catastrophic nature of global warming but in the short run at least a comparison of cost and benefits is required and in any event all decisions imply costs and benefits but what is the right figure for the social cost of carbon this paper reviews the uk government s assessment of the cost and concludes that it has been set far too high because of a misreading of the integrated assessment models used to balance costs and benefits moreover adoption of the uk government s shadow price would have formidable implications for energy policy in the uk and for policies on afforestation copyright 2003 oxford university press

distributional biases in the analysis of climate change abstract the economic analysis of global warming is dominated by models based on optimal growth theory these representative agent models have an intrinsic distributional bias in favor of the rich the bias is compounded by the use of revenue neutrality in the allocation of emission permits the result is mitigation recommendations that are biased downwards

private information wage bargaining and employment fluctuations shimer 2005 pointed out that although we have a satisfactory theory of why some workers are unemployed at any given time we don t know why the number of unemployed workers varies so much over time the basic mortensen pissarides 1994 model does not generate nearly enough volatility in unemployment for plausible parameter values this paper extends the mortensen pissarides model to allow for informational rents productivity is subject to publicly observed aggregate shocks and to idiosyncratic shocks that are seen only by the employer it is shown that there is a unique equilibrium provided that the idiosyncratic shocks are not too large the main result is that small fluctuations in productivity that are privately observed by employers can give rise to a kind of wage stickiness in equilibrium and the informational rents associated with this stickiness are sufficient to generate relatively large unemployment fluctuations

labor turnover and the natural rate of unemployment efficiency wage vs frictional unemployment wage and unemployment responses to changes in economic environment are compared for efficiency wage and frictional models changes in aggregate demand persistence of job specific shocks cost of living and unemployment benefits are considered wages and unemployment move in the same direction in the two models except that an upward shift in aggregate labor demand can reduce the real wage in the efficiency wage but not the frictional model in a numerical simulation calibrated to u s data real productivity shocks in the efficiency wage model yield a ratio of unemployment to wage variability close to that of the united states

optimal cordon pricing abstract this paper presents a simple spatial model of traffic congestion for a monocentric city to investigate the effects of cordon pricing on trip making and congestion level in each location optimal cordon pricing is obtained as a combination of the cordon location i e distance of the cordon from the cbd and the amount of toll charged there that maximizes the total social surplus in a city under optimal cordon pricing trips originating from locations inside the cordon are under priced those just outside the cordon are over priced and those near the urban fringe are under priced numerical simulations using the parameter values based on japanese data suggest that cordon pricing attains an economic welfare level very close to the first best optimum

the effects of ageing and an environmental trust fund in an overlapping generations model on carbon emission reductions most currently employed integrated assessment models for climate change are of a dynastic nature they employ the ramsey rule linking the interest rate economic growth and the rate of pure time preference this paper argues that although a dynastic framework might be convenient for economic analysis it is restrictive and can be misleading overlapping generations models which do not employ the ramsey rule are more flexible and may give results different from those derived from dynastic models with the integrated assessment model alice 2 0 it is shown how various assumptions on demographic change and public institutions can affect the interest rate thereby influencing the efficient greenhouse gas emission reductions it is concluded that dynastic integrated assessment models are in many respects inappropriate for providing policy makers with quantitative figures about the costs of carbon dioxide emissions and their desirable reduction levels 2001 elsevier science b v all rights reserved

competitive screening under heterogeneous information we study the interplay between informational frictions and second degree price discrimination our theory recognizes that consumers differ in their tastes for quality as well as in the information they possess about available offers which leads to dispersion over price quality menus in equilibrium while firms are ex ante identical we show that their menus are ordered so that more generous menus leave more surplus to consumers of all valuations we explore the cross section of equilibrium menus and variations in market conditions to generate empirical predictions on prices qualities and markups across firms and within a firm s product line for instance more competition may raise prices for low quality goods yet consumers are better off as the qualities they receive also increase the predictions of our model illuminate empirical findings in many markets such as those for cell phone plans yellow pages advertising cable tv and air travel

business cycles with worker moral hazard we consider an economy with unemployment where firms pay efficiency wages due to effort enforcement problems and face output prices that vary cyclically between a high and a low level ph and pl we show that for a range of pl ph 1 employment and the wage will be cylically rigid and that this range is greater the shorter h periods are for lower pl ph employment will vary procyclically but then also the wage and more so the more employment varies this implies a limited role for efficiency wage theory in explaining employment variations over the business cycle but a greater role for explaining productivity fluctuations according to okun s law

applications and interviews firms recruiting decisions in a frictional labour market i develop a directed search model to study the recruitment decisions of firms competing for workers who ex post differ in two dimensions 1 their match productivity and 2 their probability of accepting a job offer endogenously determined by their choice of application portfolio to attract these workers firms post a recruiting intensity and a hiring standard in addition to terms of trade a higher recruiting intensity is costly but allows the firm to select more applicants for an interview which reveals their productivity the hiring standard solves the tradeoff between immediate hiring and waiting for a potentially better match in the future i characterize equilibrium and find that various outcomes including uniqueness of equilibrium and the cyclicality of recruiting intensity crucially depend on firms recruiting cost and workers search cost calibration of the model to the u s labour market indicates a continuum of equilibria given selection of a particular equilibrium hiring standards are countercyclical while recruiting intensity is procyclical the calibrated model creates more amplification than a standard model without intensive margins and gives rise to procyclical match efficiency when viewed through the lens of a cobb douglas matching function

performance pay and adverse selection it is well known in personnel economics that firms may improve the quality of their workforce by offering performance pay we analyze an equilibrium model where worker productivity is private information and show that the firms gain from worker self selection may not be matched by a corresponding social gain in particular the equilibrium incentive contracts are excessively high powered thereby inducing the more productive workers to exert too much effort and increasing agency costs stemming from the misallocation of effort

constrained efficiency with adverse selection and directed search abstract this paper studies constrained efficiency in guerrieri et al s 2010 model of adverse selection and directed search buyers post contracts and sellers with private information about their type direct their search toward their preferred contract buyers and sellers then match bilaterally and trade if the guerrieri shimer wright equilibrium fails to achieve the first best then the planner subject to the frictions of the environment achieves strictly higher welfare than the equilibrium i e the equilibrium is not ex ante constrained efficient under certain conditions the planner achieves an allocation that even pareto dominates the equilibrium i e the equilibrium is not interim constrained efficient under other conditions the planner can completely undo the effects of adverse selection and achieves the first best cross subsidization is the key to these results

the welfare gains from pricing road congestion using automatic vehicle identification and on vehicle meters it is a widely accepted proposition that there is a general underpricing of auto travel in u s cities auto travel imposes a congestion externality with an efficient peak period level estimated at lo 23t per mile on urban freeways small 1121 2 3 but for most urban auto travel tolls consist almost entirely of the gasoline excise tax at a fuel economy of 15 miles per gallon the auto toll implied by the current high gas tax in the united states of 25e per gallon is only 1 7e per mile this is much too low for most peak period travel and even underprices some off peak travel the purpose of this study is to estimate the welfare gains which are possible under different regimes for imposing higher auto tolls in urban areas the three regimes studied are associated with a higher gas tax and systems called automatic vehicle identification and on vehicle metering the framework for the study is a model of a city whose shape is that of a wedge or pie slice of a circle the model s features include

frontiers of climate change economics the economics of climate change is an active field of research the contributions to a special issue are put in context of the literature and it is suggested that second best issues such as carbon leakage and the green paradox need to be complemented with a political economy analysis of why certain instruments are politically infeasible and with intra and intergenerational analyses of the impact of climate policy a case is also made for more empirical work on the gradual and catastrophic damages of global warming

road pricing lessons from london lessons from london this paper assesses the original london congestion charging scheme lccs and its impacts and it simulates the proposed extension which will include most of kensington and chelsea it also touches upon the political economy of the congestion charge and the increase of the charge from 5 to 8 per day the possibility of transferring the experience to paris rome and new york is also discussed the lccs has had positive impacts this was despite the considerable political influences on the charge level and location it is difficult to assess the impacts of the increase of the charge from 5 to 8 which took place in july 2005 because no data have yet been released by transport for london the proposed extension of the charging zone does not seem to be an efficient change on economic grounds at least for the specific boundaries method of charging and level of charging that is currently planned our benefit cost ratios computed under different assumptions of costs and benefits are all below unity overall the experience shows that simple methods of congestion charging though in no way resembling first best pigouvian taxes can do a remarkably good job of creating benefits from the reduction of congestion nevertheless the magnitude of these benefits can be highly sensitive to the details of the scheme which therefore need to be developed with great care georgina santos and gordon fraser

welfare specifications and optimal control of climate change an application of fund the sensitivity of the optimal control of carbon dioxide emissions to the specification of the social welfare function is systematically explored using the fund model increasing risk aversion emphasises climate change damages relative to emission reduction costs but at the same time increases the discount rate of consumption without international co operation the discount rate effect dominates so that optimal control decreases with increasing risk aversion with international co operation optimal control first increases then decreases with increasing risk aversion since climate change falls heaviest on the poor optimal control increases with increasing inequity aversion full fledged intergenerational welfare functions on the one hand emphasise climate change damages but on the other hand place more weight on current poorer generations in fund the two tendencies almost cancel

second best congestion pricing schemes in the monocentric city abstract this paper considers second best congestion pricing in the monocentric city with endogenous residential density and endogenous labour supply a spatial general equilibrium model is developed that allows consideration of the three way interactions between urban density traffic congestion and labour supply congestion pricing schemes are analysed that are second best by design and not because distortions exist elsewhere in the spatial economy like cordon charging and flat kilometre charges both for cobb douglas utility and for ces utility the analyses suggest that the relative welfare losses from second best pricing compared to first best pricing are surprisingly small

the optimal research and development portfolio of low carbon energy technologies a study of china to support decision making for an optimal portfolio strategy for low carbon energy technology research and development r d this study proposes a dynamic two stage stochastic programming model taking into account both the uncertainty of technological change and damages of climate change based on china s economic and technology level and expert elicitation an r d investment portfolio strategy looking at three low carbon technologies carbon capture and storage ccs solar photovoltaic pv and nuclear including nine projects is investigated through the proposed model the optimized results show that the optimal r d technology portfolio is robust to different levels of risk in climate damage however the total social costs for the optimal r d technology portfolio is lowest in the medium risk of climate damage scenario under different opportunity costs the composition of the optimal r d portfolio varies however projects for each of the three technologies always constitute the optimal r d portfolio furthermore the implication is that a technology synergistic r d strategy is conducive to enhancing the level of co2 abatement and reducing the total social cost

policy analysis of the greenhouse effect an application of the page model abstract in this paper we introduce a comprehensive model for policy analysis of the greenhouse effect page we apply the page model to assess the merits of policies to prevent global warming by controlling the emissions of greenhouse gases and policies to adapt to any global warming that occurs the results confirm that it is difficult to overcome the problem of global warming by taking preventive action alone the argument for introducing an aggressive adaptive policy is very strong we calculate the valuation that would have to be placed upon non economic environmental and social impacts for a combined strategy of preventive and adaptive policies to be considered a worthwhile option both for individual regions and for the world as a whole we also show that uncertainties in all four groups of inputs to the model scientific costs of control costs of adaptation and valuation of impacts have a great influence on the costs and impacts of the combined strategy

a general equilibrium analysis of climate change impacts on tourism this paper studies the economic implications of climate change induced variations in tourism demand using a world cge model the model is first re calibrated at some future years obtaining hypothetical benchmark equilibria which are subsequently perturbed by shocks simulating the effects of climate change we portray the impact of climate change on tourism by means of two sets of shocks occurring simultaneously the first set of shocks translate predicted variations in tourist flows into changes of consumption preferences for domestically produced goods the second set reallocate income across world regions simulating the effect of higher or lower tourists expenditure our analysis highlights that variations in tourist flows will affect regional economies in a way that is directly related to the sign and magnitude of flow variations at a global scale climate change will ultimately lead to a welfare loss unevenly spread across regions 2005 elsevier ltd all rights reserved

do current assessments underestimate future damages from climate change while the economic debate on climate policy focuses on discounting we do not know yet what to discount the potential non discounted socio economic cost of climate change indeed is still unknown only a few studies have tried to estimate socio economic costs of climate change most of them concluded that for a warming of a few degrees damages will be limited to a few percent of gdp all these studies however have disregarded important mechanisms and have only considered the cost of a stabilized new climate this article claims that the climate change issue should instead be framed in terms of the adaptation of socio economic systems to a changing climate doing so it calls for the taking into account of 1 the interaction between the uncertainty on future climate and the inertia of important economic sectors 2 the short term economic constraints that will be key in the response to climate shocks finally the impacts of climate change cannot be estimated assuming that societies will always be able to manage in a perfect way the subsequent change in risks as past experiences demonstrate our poor ability to do so these mechanisms suggest that the uncertainty on future climate change damages is even larger than is usually acknowledged and calls for additional research on climate change impacts

equitable cost benefit analysis of climate change greenhouse gas emissions and vulnerability to climate change show a strong negative correlation this is the moral issue at the heart of the climate problem however little attention has been paid to this in the literature see banuri et al 1996 for an overview the literature on equity issues in climate change is largely confined to the distribution of emissions reduction targets this literature takes the need to reduce greenhouse gas emissions for granted and takes a parametric approach to the required reductions on the other hand the literature that tries to derive how much emissions abatement is desirable largely ducks the equity issue this paper is an attempt to combine the two problems

on revenue recycling and the welfare effects of second best congestion pricing in a monocentric city abstract this paper examines congestion taxes in a monocentric city with pre existing labor taxation when road toll revenue is used to finance labor tax cuts 35 of the optimal road tax in our numerical model does not reflect marginal external congestion costs but rather functions as a ramsey mirrlees tax i e an efficiency enhancing mechanism allowing for an indirect spatial differentiation of the labor tax this adds a quite different motivation to road pricing since welfare gains can be produced even in absence of congestion we find that the optimal road tax is non monotonic across space reflecting the different impacts of labor supply elasticity and marginal utility of income which both vary over space the relative efficiencies of some archetype second best pricing schemes cordon toll flat kilometer tax are high 84 and 70 respectively when road toll revenue is recycled lump sum the optimal toll lies below its pigouvian level extensions in a bimodal framework show that the optimality of using road toll revenue to subsidize public transport depends on the initial inefficiency in public transport pricing

second best congestion pricing the case of an untolled alternative abstract this paper deals with second best one route congestion pricing in case of an untolled alternative using a two link network simulation model the effects of various demand and cost parameters on the relative efficiency of one route tolling are analyzed it is investigated whether the existence of costs of congestion charging may be a reason for one route tolling to be more overall efficient than two route tolling finally the efficiency of revenue maximizing one route and two route tolling is discussed

designing climate mitigation policy this us paper provides an exhaustive review of critical issues in the design of climate mitigation policy by pulling together key findings and controversies from diverse literatures on mitigation costs damage valuation policy instrument choice technological innovation and international climate policy the authors begin with the broadest issue of how high assessments suggest the near and medium term price on greenhouse gases would need to be both under cost effective stabilization of global climate and under net benefit maximization or pigouvian emissions pricing the remainder of the paper focuses on the appropriate scope of regulation issues in policy instrument choice complementary technology policy and international policy architectures

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

on international equity weights and national decision making on climate change abstract estimates of the marginal damage costs of carbon dioxide emissions require the aggregation of monetised impacts of climate change over people with different incomes and in different jurisdictions implicitly or explicitly such estimates assume a social welfare function and hence a particular attitude towards equity and justice we show that previous approaches to equity weighting are inappropriate from a national decision maker s point of view because domestic impacts are not valued at domestic values we propose four alternatives sovereignty altruism good neighbour and compensation with different views on concern for and liability towards foreigners the four alternatives imply radically different estimates of the social cost of carbon and hence the optimal intensity of climate policy

optimal dynamic carbon taxes in a climate economy model with distortionary fiscal policy how should carbon be taxed as a part of fiscal policy the literature on optimal carbon pricing often abstracts from other taxes however when governments raise revenues with distortionary taxes carbon levies have fiscal impacts while they raise revenues directly they may shrink the bases of other taxes e g by decreasing employment this article theoretically characterizes and then quantifies optimal carbon taxes in a dynamic general equilibrium climate economy model with distortionary fiscal policy first this article establishes a novel theoretical relationship between the optimal taxation of carbon and of capital income this link arises because carbon emissions destroy natural capital they accumulate in the atmosphere and decrease future output consequently this article shows how the standard logic against capital income taxes extends to distortions on environmental capital investments second this article characterizes optimal climate policy in sub optimal fiscal settings where income taxes are constrained to remain at their observed levels third this article presents a detailed calibration that builds on the seminal dice approach but adds features essential for a setting with distortionary taxes such as a differentiation between climate change production impacts e g on agriculture and direct utility impacts e g on biodiversity existence value the central quantitative finding is that optimal carbon tax schedules are 8 24 lower when there are distortionary taxes compared to the setting with lump sum taxes considered in the literature

holdups and efficiency with search frictions a natural holdup problem arises in a market with search frictions firms have to make a range of investments before finding their employees and larger investments translate into higher wages in particular when wages are determined by ex post bargaining the equilibrium is always inefficient recognizing that capital intensive production relations have to pay higher wages firms reduce their investments this can only be prevented by removing all the bargaining power from the workers but this in turn depresses wages below their social product and creates excessive entry of firms in contrast to this benchmark we show that efficiency is achieved when firms post wages and workers can direct their search toward more attractive offers this efficiency result generalizes to an environment with imperfect information where workers only observe a few of the equilibrium wage offers we show that the underlying reason for efficiency is not wage posting per se but the ability of workers to direct their search toward more capital intensive jobs

competitive pricing and efficiency in search equilibrium we consolidate and generalize some results on price determination and efficiency in search equilibrium extending models by rubinstein and wolinsky and by gale heterogeneous buyers and sellers meet according to a general matching technology and prices are determined by a general bargaining condition when the discount rate r and search costs converge to 0 we show that prices in all exchanges are the same and equal the competitive market clearing price given positive search costs efficiency obtains iff bargaining satisfies hosios condition and r 0 when prices are set by third party market makers however we show that search equilibrium is necessarily efficient

heterogeneity job creation and unemployment volatility in this paper i explore the impact of match specific heterogeneity at the job creation margin on business cycle fluctuations i show that this form of heterogeneity alone does not help to amplify labor market volatility either under full or under asymmetric information first i show analytically that under full information heterogeneity has no first order effect on the response of unemployment and job creation to productivity and actually tends to dampen the response of market tightness then in a series of calibrations i show that with both full and asymmetric information the model delivers labor market volatilities close to the representative agent full information benchmark

taxes and quotas for a stock pollutant with multiplicative uncertainty we compare taxes and quotas when firms and the regulator have asymmetric information about the slope of firms abatement costs damages are caused by a stock pollutant we calibrate the model using cost and damage estimates of greenhouse gasses taxes dominate quotas as with additive uncertainty this model with multiplicative uncertainty allows us to compare expected stock levels under the two policies and to investigate the importance of stock size and the magnitude of uncertainty on the policy ranking

the economic effects of climate change greenhouse gas emissions are fundamental both to the world s energy system and to its food production the production of co2 the predominant gas implicated in climate change is intrinsic to fossil fuel combustion specifically thermal energy is generated by breaking the chemical bonds in the carbohydrates oil coal and natural gas and oxidizing the components to co2 and h2o one cannot have cheap energy without carbon dioxide emissions similarly methane ch4 emissions an important greenhouse gas in its own right are necessary to prevent the build up of hydrogen in anaerobic digestion and decomposition one cannot have beef mutton dairy or rice without methane emissions climate change is the mother of all externalities larger more complex and more uncertain than any other environmental problem the sources of greenhouse gas emissions are more diffuse than any other environmental problem every company every farm every household emits some greenhouse gases the effects are similarly pervasive weather affects agriculture energy use health and many aspects of nature which in turn affects everything and everyone the causes and consequences of climate change are very diverse and those in low income countries who contribute least to climate change are most vulnerable to its effects climate change is also a long term problem some greenhouse gases have an atmospheric life time measured in tens of thousands of years the quantities of emissions involved are enormous in 2000 carbon dioxide emissions alone and excluding land use change were 24 billion metric tons of carbon dioxide tco2

policy v individual heterogeneity in the benefits of climate change mitigation evidence from a stated preference survey abstract we use stated preference methods to investigate the public s preferences for decarbonization policies we ask three research questions first does the willingness to pay wtp for each ton of co2 emissions reductions depend on the policies and on individual characteristics of the respondents second how extensive is the variation associated with these factors third what factors affect support for or opposition to a carbon tax based on the responses to discrete choice experiments from a sample of italians we find that the wtp per ton of co2 ranges between zero and 230 the variation associated with the policy instrument is approximately of the same order of magnitude as that associated with individual characteristics of the respondents

the impact of climate change on the balanced growth equivalent an application of fund the stern review added balanced growth equivalents bge to the economic climate change research agenda we first propose rigorous definitions of the bge for multiple regions and under uncertainty we show that the change in the bge is independent of the assumed scenario of per capita income for comparable welfare economic assumptions as the stern review we calculate lower changes in bge between a business as usual scenario and one without climate impacts with the model fund than the stern review found with the model page we find that mitigation policies give even lower changes in bge and argue that those policy choices should be the focus of the research effort rather than total damage estimates according to our results the current carbon tax should be below 55 tc sensitivity analyses show that the stern review chose parameters that imply high impact estimates however for regionally disaggregated welfare functions we find changes in bge that are significantly higher than the results from the stern review both for total damage as for policy analysis with regional disaggregation and high risk aversion we observe fat tails and with that very high welfare losses

the damage costs of climate change toward more comprehensive calculations it is argued that estimating the damage costs of a certain benchmark climate change is not sufficient what is needed are cost functions and confidence intervals although these are contained in the integrated models and their technical manuals this paper brings them into the open in order to stimulate discussion after briefly reviewing the benchmark climate change damage costs region specific cost functions are presented which distinguish tangible from intangible losses and the losses due to a changing climate from those due to a changed climate furthermore cost functions are assumed to be quadratic as an approximation of the unknown but presumably convex functions results from the damage module of the integrated climate economy model fund are presented next uncertainties are incorporated and expected damages are calculated it is shown that because of convex loss functions and right skewed uncertain ties the risk premium is substantial calling for more action than analysis based on best guess estimates the final section explores some needs for further scientific research

the damage costs of climate change towards a dynamic representation economic assessments of climate change impacts are commonly presented as the effect of a climate change associated with a doubling of the atmospheric concentration of carbon dioxide on the current economy this paper is an attempt to express impact as a function of both climate change and socio economic change with regard to climate change issues discussed are level versus rate of change speed of adaptation speed of restoration and value adjustment and symmetry with regard to socio economic change agriculture migration and the valuation of intangible losses are addressed uncertainty and higher order impacts are treated briefly it is qualitatively argued and quantitatively illustrated that these issues matter a great deal for the damage profile over the next century a damage model based on my best guesses is presented in the appendix

a theory of commerce abstract the theory of commerce advanced here captures prominent features of retail trade large employment congestion effects anonymous posted prices and quantity discounts this theory is built around a directed search model where buyers preferences are private information the analytical solution is easily inserted in a neoclassical growth framework in this framework the parameters of retail trade are calibrated using commercial margins and employment welfare properties depend on the sellers ability to charge two tier prices with two tier prices the directed search equilibrium is efficient otherwise it is not this contrasts with the full information benchmark where directed search is always efficient

how much damage will climate change do recent estimates two reasons to be concerned about climate change are its unjust distributional impact and its negative aggregate effect on economic growth and welfare although our knowledge of the impact of climate change is incomplete and uncertain economic valuation is difficult and controversial and the effect of other developments on the impacts of climate change is largely speculative the authors find that poorer countries and people are more vulnerable than are richer countries and people a modest global warming is likely to have a net negative effect on poor countries in hot climates but may have a net positive effect on rich countries in temperate climates if one counts dollars the world aggregate may be positive if one counts people the world aggregate is probably negative negative impacts would become more negative and positive impacts would turn negative for more substantial warming the marginal costs of carbon dioxide emissions are uncertain and sensitive to assumptions that partially reflect ethical positions but are unlikely to be larger than 50 per tonne carbon

equilibrium incentive contracts and efficiency wages we analyze the optimal efficiency wage contract when output is contractible but firms neither observe the workers effort nor their match specific productivity firms offer wage contracts that optimally trade off effort and wage costs as a result employed workers enjoy rents which in turn creates unemployment nonetheless the incentive power of the equilibrium wage contract is constrained efficient in the absence of taxes and unemployment benefits we also show that more high powered incentive contracts tend to be associated with higher equilibrium unemployment rates jel e24 j30 j41

economy wide estimates of the implications of climate change sea level rise the economy wide implications of sea level rise in 2050 are estimated using a static computable general equilibrium model this allows for a better estimate of the welfare effects of sea level rise than the common direct cost estimates and for an estimate of the impact of sea level rise on greenhouse gas emissions overall general equilibrium effects increase the welfare costs of sea level rise but not necessarily in every sector or region in the absence of coastal protection economies that rely most on agriculture are hit hardest although energy is substituted for land overall energy consumption falls with the shrinking economy hurting energy exporters with full coastal protection gdp increases particularly in regions with substantial dike building but utility falls least in regions that protect their coasts and export energy energy prices rise and energy consumption falls the costs of full protection exceed the costs of losing land the results also show direct costs the usual method for estimating welfare changes due to sea level rise are a bad approximation of the general equilibrium welfare effects previous estimates of the economic impact of sea level rise are therefore biased

on the job search and moral hazard we analyze the interaction between intertemporal incentive contracts and search frictions associated with on the job search in our model agency problems call for wage contracts with deferred compensation at the same time workers do on the job search deferred compensation improves workers incentives to exert effort but distorts their on the job search decisions we show that deferred compensation is less attractive when the value to the worker firm pair of on the job search is high moreover the interplay between search frictions and wage contracts creates feedback effects if firms in equilibrium use contracts with deferred compensation fewer firms with vacancies enter the on the job search market and this in turn reduces the distortions created by deferred compensation these feedback effects between the incentive contracts used and the activity level in the search markets can lead to multiple equilibria a low turnover equilibrium where firms use deferred compensation and a high turnover equilibrium where they do not furthermore the model predicts that firms are more likely to use deferred compensation when search frictions are high and when the gains from on the job search are small

the value of adaption climate change and timberland management abstract adaptation to exogenous change occurs on both intensive and extensive margins whether and how one accounts for human adaptation directly affects estimates of the economic consequences of environmental change estimates that are both critical in informing policy decisions and notoriously difficult to value this paper introduces and applies an analytical framework for placing an economic value on adaptation we explore the issue first in a stylized model that facilitates making concrete generalizations about the kinds of adaptations that generate high or low economic value we then test the soundness of our insights by incorporating learning and adaptive decision making into a structural dynamic forestry model where climate change is imposed exogenously and agents respond optimally using downscaled climate projections integrated with site and species specific timber productivity data we estimate the economic value of adaptation to climate change within the california timber industry we find on the intensive margin changing the rotation intervals will yield a low value of adaptation but on the extensive margin replanting more suitable tree species can yield significant value

discounting and distributional considerations in the context of global warming the economics of global warming is reviewed with special emphasis on how the cost depends on the discount rate and on how costs in poor and rich regions are aggregated into a global cost estimate both of these factors depend on the assumptions made concerning the underlying utility and welfare functions it is common to aggregate welfare gains and losses across generations and countries as if the utility of money were constant but it is not if we assume that a e co2 equivalent dlubling implies costs equal to 1 5 of the income in both high and low income countries a pure rate of time preference equal to zero and a utility function which is logarithmic in income then the marginal cost of co2 emissions is estimated at 260 590 usd ton c for a time horizon in the range 300 1000 years an estimate which is large enough to justify significant reductions of co2 emissions on purely economic grounds the estimate is approximately 50 100 times larger than the estimate made by nordhaus in his dice model and the difference is almost completely due to the choice of discount rate and the weight given to the costs in the developing world as well as a more accurate model of the carbon cycle finally the sensitivity of the marginal cost estimate with respect to several parameters is analyzed

monetary valuation of the social cost of co2 emissions a critical survey an expanding branch of research has estimated the potential costs of climate change which are often expressed as the social cost of carbon scc or the costs of an additional ton of co2 emissions estimates of the scc can be used by policy makers to evaluate climate change policies and greenhouse gas emission reduction projects by means of cost benefit analyses cbas such analyses are complicated by the wide range of scc values that have been reported in the literature and the large uncertainties involved in estimating the potential economic impacts and related costs of climate change this study presents a critical review of the reported scc estimates by examining some neglected consequences of climate change uncertain and extreme scenarios of climate change the discounting of future climate change effects the treatment of individual risk aversion and assumptions about social welfare in view of the many uncertainties and omissions in conventional cost benefit analyses of climate impacts and the scc alternative approaches to decision making should be considered for climate policy

climate change costs recent advancements in the economic assessment climate change is unique among the consequences of fossil fuel burning in its far reaching impact both spatially and temporally earlier studies estimate the aggregated monetized damage due to climate change at 1 5 to 2 0 of world gdp for 2 co2 the oecd would lose 1 0 to 1 5 of gdp the developing countries 2 0 to 9 0 according to these estimates these figures are not comprehensive and highly uncertain newer studies increasingly emphasize adaptation variability extreme events other non climate change stress factors and the need for integrated assessment of damages as a result differences in impacts between regions and sectors have increased the market impacts in developed countries tended to fall and non market impacts have become increasingly important marginal damages are more interesting from a policy point of view earlier estimates range from about us 5 to us 125 per tonne of carbon with most estimates at the lower end of this range these figures are based on polynomial functions in the level of climate change but the rate of change may be equally important as are the speed of adaptation restoration and value adjustment furthermore future vulnerability to climate change will be different from current vulnerability on the whole the market impacts fall relatively with economic growth while the non market impacts rise relatively with growth

a social cost of carbon for almost every country this paper uses imputed national climate change impact functions to estimate national social costs of carbon which are largest in poor countries with large populations the national social costs of carbon of faster growing economies are less sensitive to the pure rate of time preference and more sensitive to the rate of risk aversion the pattern of national social costs of carbon is not sensitive to the assumed impact function climate sensitivity and scenario although the global social cost of carbon is income convergence raises the national social costs of carbon of poorer countries and lowers them for richer countries both global and national social costs of carbon are most sensitive to the income elasticity of climate change impacts a parameter about which we know little

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

cordon pricing and land use regulation this study explores the simultaneous imposition of cordon pricing and land use regulations in a continuous and closed monocentric city with homogeneous households results reveal the optimal level of a single cordon toll and its location and the optimal floor area ratio far regulation clarifying what distortions remain in the existence of cordon pricing and far regulation among other results this paper shows that with an optimal cordon toll far regulation should alternate between a minimum and a maximum regulation both inside and outside the cordon line

embodied technical change and the fluctuations of unemployment and wages a matching model where technological change is partially embodied in the job match is shown to be successful in explaining the variability of unemployment and vacancies if we incorporate long term wage contracts into the model it also explains a number of stylized facts on the dynamics of real wages which have been found in the empirical labor literature

cooperation on climate change mitigation abstract we analyze conditions under which it is possible to achieve efficient mitigation of greenhouse gas emissions with a self enforcing international agreement in which all countries find it in their self interest to abide by the agreement we model the choice of emissions by countries as a dynamic game we use a two part punishment scheme for deviations from an agreement that is renegotiation proof and show when this scheme supports the efficient outcome as a subgame perfect equilibrium using numerical examples we show that an efficient subgame perfect equilibrium exists for a range of reasonable parameter values the existence of such equilibrium may be non monotonic in the discount rate and the ratio of slope of marginal abatement cost and marginal damages

the general equilibrium effects of congestion externalities abstract this is the second in a series of three articles on the topic of congestion externalities we use an urban general equilibrium model to compute two types of cities the market equilibrium city in which congestion externalities occur and the optimum city the optimum city has a more dispersed distribution of employment and a more concentrated distribution of residence if the population of the city is fixed the optimum pricing of transportation generates a per capita welfare gain of 3 78 per week if the population of the city is endogenous the internalization of congestion externalities causes the city to grow

incentives in competitive search equilibrium this paper proposes a labor market model with job search frictions where workers have private information on match quality and eort firms use wage contracts to motivate workers in addition wages are also used to attract employees we de ne and characterize competitive search equilibrium in this context and show that it satis es a simple modi ed hosios rule the model is used to address the shimer puzzle related to the low volatility of the unemployment rate relative to the volatility of output observed in the data we nd that private information may increase the responsiveness of the unemployment rate to changes in productivity and in particular to changes in

congestion land use and job dispersion a general equilibrium model abstract in dispersed cities congestion tolls would drive up central wages and rents and would induce centrally located producers to want to disperse closer to their workers and their customers paying lower rents and realizing productivity gains from land to labor substitution but the tolls would also induce residents to want to locate more centrally in order to economize on commuting and shopping travel in a computable general equilibrium model we find that the centralizing effect of tolls on residences dominates on the decentralizing effect of tolls on firms causing the dispersed city to have more centralized job and population densities under stylized parameters we find that efficiency gains from levying congestion tolls on work and shopping travel are 3 0 of average income about 80 of such gains come from road planning and 20 from tolls

motivation and markets many workers receive pay based on subjectively assessed performance yet the shirking model of efficiency wages excludes it this paper incorporates such pay with the following results performance pay is more efficient than efficiency wages when the costs of having a job vacant are low and qualified workers in short supply more capital intensive industries pay more than less capital intensive industries as observed in studies of interindustry wages differentials sustaining an efficient outcome requires a social convention similar to the notion of a fair wage the model also makes predictions about the relationship between turnover wages growth and unemployment copyright 1998 by american economic association

targets for global climate policy an overview a survey of the economic impact of climate change and the marginal damage costs shows that carbon dioxide emissions are a negative externality the estimated pigou tax and its growth rate are too low to justify the climate policy targets set by political leaders a lower discount rate or greater concern for the global distribution of income would justify more stringent climate policy but would imply an overhaul of other public policies catastrophic risk justifies more stringent climate policy but only to a limited extent

climate change and insurance a critical appraisal several issues relating to insurance and the damage costs of climate change are discussed it is argued that the option of insuring climate change is severely limited because the associated damages are hardly quantifiable and little diversifiable in addition binding contracts are a problem on long time scales and in an international context hedging consumption smoothing over time precautionary investments and liability are not to be presented under the heading of insurance not only because this unnecessarily and confusingly expands the traditional definition of insurance but also because this could create a false sense of security the impact of climate change on the profitability of the commercial insurance sector is not likely to be severe as the insurance companies are capable of shifting changed risks to the insured provided that they are properly and timely informed on the consequences of climate change

efficient unemployment insurance this paper constructs a tractable general equilibrium model of search with risk aversion an increase in risk aversion reduces wages unemployment and investment unemployment insurance has the opposite effect insured workers seek high wage jobs with high unemployment risk an economy with risk neutral workers achieves maximal output without any unemployment insurance but an economy with risk averse workers requires a positive level of unemployment insurance to maximize output therefore moderate unemployment insurance not only improves risk sharing but also increases output