environmental protection rare disasters and discount rates the stern review s evaluation of environmental protection stresses low discount rates and uncertainty about environmental effects an appropriate model for analysing this uncertainty and the associated discount rates requires sufficient risk aversion and fat tailed uncertainty to account for the observed equity premium calibrations based on epstein zin preferences and existing analyses of rare macroeconomic disasters suggest that optimal environmental investment can be a significant share of gdp even with reasonable rates of time preference optimal environmental investment increases with risk aversion and the probability and typical size of environmental disasters but decreases with uncertainty about policy effectiveness

best policy response to environmental shocks applying a stochastic framework abstract the paper develops a general framework for the analysis of environmental shocks in growing economies endogenous capital investments allow identifying the dual role of capital as a buffer against shocks and a source of pollution we study the effects of recurring natural disasters on optimal growth and efficient environmental policies emissions may cause continuous fluctuations entail discrete and recurring jumps or trigger so called tipping points with large costs to the economy closed form solutions are provided for all the model variants we discuss possible applications in environmental economics and identify current research gaps

dynamic cournot duopoly with intertemporal capacity constraints this paper studies a dynamic cournot duopoly in which suppliers have a limited amount of products available for two consecutive periods we derive optimal sales strategies and analyze welfare effects with and without commitment under commitment strategies do not depend on the rival s realized sales in this case there is a unique nash equilibrium for any allocation of initial supplies and prices increase over time absent commitment sellers can adjust their supply decision after the first period in this case a subgame perfect nash equilibrium does not always exist and prices may decline over time a more asymmetric allocation of stocks generally leads to higher first period prices whereas the impact on second period prices is ambiguous the larger firm typically prefers not to commit whereas the smaller firm is better off under commitment commitment generates a higher total surplus and almost always a higher consumer surplus our findings thus suggest that market transparency or flexible supply contracts can adversely affect welfare in situations where production precedes sales and firms face an intertemporal capacity constraint

sunk costs and strategic commitment a proposed three stage equilibrium dixit s i980 paper in this journal the role of investment in entry deterrence has attracted considerable interest from economists concerned with constructing a modern theory of strategic behaviour towards entry in fact the paper has spawned quite an industry of commitment models in which the equilibrium payoffs in some final period game can be influenced by strategic commitments made by the players in an earlier period for similar models with important insights into strategic entry deterrence see eaton and lipsey i980 i98i schmalensee i98i the purpose of this note is to argue that when the instrument of stragetic commitment takes the form of sunk costs which both entrant and incumbent have to bear as it does in dixit s paper and in many other examples a three stage model rather than the two stage model presented by dixit is required although the proposed equilibrium differs from dixit s its qualitative features are the same it may or may not be profitable to deter entry and if it is the first mover may still prefer to play an accommodation strategy and allow entry to take place following dixit we restrict our attention to the asymmetric case in which one firm the incumbent makes the first move the two stage game involves the first mover sinking part of its costs in advance so that in the second stage equilibrium it will have a current cost advantage over the entrant which must incur the full cost of producing any desired output level the second period cost asymmetry ensures the incumbent a lar ger share of the post entry market which may be sufficient to deter entry altogether the problem with the two stage game lies in the nature of sunk costs sunk costs by definition are committed before the production period takes place if they were expended as a flow simultaneously with production they would not be sunk the installation of capacity is the natural example employed by dixit and well illustrates the point if installed capacity is a sunk cost which it must be for the incumbent to acquire any strategic advantage at all then the entrant s installed capacity is equally sunk and must also be committed before the production period takes place given this observation the post entry final period equilibrium should not be modelled as if the entrant were simultaneously incurring both variable and sunk costs but the incumbent only incurs variable costs this implies too great an asymmetry in favour of the incumbent the final period equilibrium should involve both firms incurring only variable

a social and environmental approach to microfinance credit scoring microfinance institutions provide loans to low income individuals their credit scoring systems if they exist are strictly financial although many institutions consider the social and environmental impact of their loans they do not incorporate formal systems to estimate these social and environmental impacts this paper proposes that their creditworthiness evaluations should be coherent with their social mission and accordingly should estimate the social and environmental impact of microcredit thus a decision support system to facilitate microcredit granting is proposed using a multicriteria evaluation the assessment of social impact is performed by calculating the social net present value the system captures credit officers experience and addresses incomplete and intangible information the model has been tested in a microfinance institution the paper shows how a small institution can include social and environmental issues in its decision making systems to evaluate credit applications a gap in the preferences was found between members of the board who are socially driven and managers and credit officers who are financially drifted this mission drift was corrected the approach followed contributed to creating a culture of social and environmental assessment within the institution especially among credit officers thereby translating microfinance institutions social mission into numbers

on the size distribution of macroeconomic disasters confidence interval of 2 to 4 the results are robust to uncertainty about the values of the disaster probability and the equity premium and can accommodate seemingly paradoxical situations in which the equity premium may appear to be infinite

bertrand competition with subcontracting we investigate how the possibility of subsequently subcontracting production to each other influences rivals initial competition for a contract or a market as a two stage game in its first stage the two firms engage in price competition to supply a contract or a market in the second stage the firms may subcontract production to each other it is supposed that the firms produce the identical product with the same strictly convex cost function the incentive for subcontracting comesfrom the strictly convex production costs a firm is obliged to supply the entire quantity demanded at its quoted price our analysis discloses that if the winner of the game s first stage determines the terms of the subcontract in its second stage there exists a unique subgame perfect nash equilibrium spne in pure strategies in which the firms bid the same price in the first stage and both receive zero profits on the other hand if the loser of the game s first stage sets the terms of the subcontract in the second stage there exists a unique spne in pure strategies in which the firms bid the same price in the first stage and both receive positive profits the presence of the possibility of subcontracting supports a unique spne in pure strategies even though no actual subcontracting may occur the spne price is below the socially optimal price in the first case and is above it in the second case we also consider other modes of sharing the gains from subcontracting between the two firms such as the nash bargaining solution

a theory of market structure with sequential entry this article sets out a theory of market structure with sequential entry we characterize the perfect nash equilibrium to the entry game in several propositions first equilibria never involve excess capacity second a sufficient statistic for the entry of any firm is that its profits are positive when computed myopically i e with no further entry third the equilibrium number of firms is the smallest number that can deter entry fourth aggregate output in equilibrium is no smaller than the limit output we calculate some explicit solutions to the model and examine comparative static properties

managing catastrophic climate risks under model uncertainty aversion we propose a robust risk management approach to deal with the problem of catastrophic climate change that incorporates both risk and model uncertainty using an analytical model of abatement we show how aversion to model uncertainty influences the optimal level of mitigation we disentangle the role of preferences from the structure of model uncertainty which we define by means of a simple measure of disagreement across models with data from an expert elicitation about climate change catastrophes we quantify the relative importance of these two effects and calibrate a numerical integrated assessment model of climate change the results indicate that the structure of model uncertainty and specifically how model disagreement varies in abatement is the key driver of optimal abatement and that model uncertainty warrants a higher level of climate change mitigation this paper was accepted by manel baucells decision analysis

climate tipping and economic growth precautionary capital and the price of carbon the optimal reaction to a climate tipping point that becomes more imminent with global warming is to be precautionary in adjusting capital to prepare for the calamity and to price carbon to make catastrophic change less imminent the saving response can be positive or negative if the mean lag for the impact of the catastrophe is long enough the saving response will be negative because the precautionary return in the keynes ramsey rule becomes negative we also show the separate effects of the elasticity of intertemporal substitution eis and the relative risk aversion rra using duffie epstein preferences focusing on a productivity catastrophe we calibrate our model and show how sensitive the policy responses are to the degrees of eis and rra the trend rate of economic growth the hazard rate and how long it takes for the catastrophe to have its full impact

evaluating risky consumption paths the role of intertemporal substitutability abstract in dynamic stochastic welfare comparisons a failure clearly to distinguish between risk aversion and intertemporal substitutability can result in misleading assessments of the impact of risk aversion on the welfare costs of consumption risk changes the problem arises in any setting in which uncertainty is propagated over time notably but not exclusively in economies with stochastic consumption trends regardless of the preference setup adopted an increase in risk aversion amplifies the per period costs of risks the weights consumers use to cumulate the per period costs of risks with persistent effects should however depend on intertemporal substitutability as well as on risk aversion under time separable expected utility preferences an increase in the period utility function s curvature therefore alters the welfare effect of risk for reasons that are in part unrelated to risk aversion to illustrate these points i reconsider lucas s estimate of the cost of consumption instability for the postwar united states

a review of the stern review on the economics of climate change the stern review calls for immediate decisive action to stabilize greenhouse gases because the benefits of strong early action on climate change outweighs the costs the economic analysis supporting this conclusion consists mostly of two basic strands the first strand is a formal aggregative model that relies for its conclusions primari ly upon imposing a very low discount rate concerning this discount rate aspect i am skeptical of the review s formal analysis but this essay points out that we are actual ly a lot less sure about what interest rate should be used for discounting climate change than is commonly acknowledged the review s second basic strand is a more intuitive argument that it might be very important to avoid possibly large uncertain ties that are difficult to quantify concerning this uncertainty aspect i argue that it might be recast into sound analytical reasoning that might justify some of the review s conclusions the basic issue here is that spending money to slow global warming should perhaps not be conceptualized primarily as being about consump tion smoothing as much as being about how much insurance to buy to offset the small change of a ruinous catastrophe that is difficult to compensate by ordinary savings

rare disasters asset prices and welfare costs a representative consumer model with epstein zin weil preferences and i i d shocks including rare disasters accords with observed equity premia and risk free rates if the coefficient of relative risk aversion equals 3 4 if the intertemporal elasticity of substitution exceeds one an increase in uncertainty lowers the price dividend ratio for equity and a rise in the expected growth rate raises this ratio calibrations indicate that society would willingly reduce gdp by around 20 percent each year to eliminate rare disasters the welfare cost from usual economic fluctuations is much smaller though still important corresponding to lowering gdp by about 1 5 percent each year

epstein zin utility in dice is risk aversion irrelevant to climate policy climate change involves uncertain probabilities of catastrophic risks and very longterm consequences of current actions climate economics therefore is centrally concerned with the treatment of risk and time yet conventional assumptions about utility and optimal economic growth create a perverse connection between risk aversion and time preference such that more aversion to current risks implies less concern for future outcomes and vice versa the same conflation of risk aversion and time preference leads to the equity premium puzzle in finance a promising response to the equity premium puzzle the recursive utility of epstein and zin allows separation of risk aversion and time preference at the cost of considerable analytic complexity we introduce an accessible implementation of epstein zin utility into the dice model of climate economics creating a hybrid ez dice model using epstein zin parameters from the finance literature and climate uncertainty parameters from the science literature we find that the optimal climate policy in ez dice calls for rapid abatement of carbon emissions it is similar to standard dice results with the discount rate set to equal the risk free rate of return ez dice solutions are sensitive to the intertemporal elasticity of substitution but remarkably insensitive to risk aversion insensitivity to risk aversion may reflect the difficulty of modeling catastrophic risks within dice implicit in dice are strong assumptions about the cost of climate stabilization and the certainty and speed of success under these assumptions risk aversion would in fact be unimportant a more realistic analysis will require a subtler treatment of catastrophic climate risk

preemptive investment with resalable capacity we study an entry game under perfect information with the salient feature that capacity is resalable we show that an inability to precommit to final output can help rather than hurt in contrast to other analyses of limited commitment e g maskin tirole 1988 which do not specify the sources of or reasons for limits to commitment we assume that such limits arise from the resalable nature of capacity and are led naturally to a consideration of additional strategic variables that can improve the incumbent s position in our model resalability increases the complexity of the incumbent s precommitment problem but it also furnishes her with an additional source of power in our model the price at which to resell capacity while a capacity resale market enables capacity to be shared and can help anticompetitive behavior the very existence of a resale market can generate an incentive for a much larger initial level of investment to the point where the overall equilibrium outcome can be more competitive

technological competition uncertainty and oligopoly abstract in an oligopoly context the present technological choice of a firm which expects to receive private revelant information just prior to the uncertain market stage has both a flexibility value and a strategic commitment value in contrast to some common wisdom ideas we provide a natural two stage competition framework in which an increase in uncertainty always raises the commitment value of the technological choice of the firm and may decrease its flexibility value when the increased uncertainty takes the form of more variable beliefs the first result tends to reinforce therefore the findings of the strategic commitment literature under certainty

spatial linkages and export processing location in china this paper provides empirical evidence that spatial linkages matter for the localisation of global value chain activities relying on processing trade data for chinese provinces during the period 1997 2008 we investigate whether a chinese province s proximity to international suppliers and international buyers within an industry chain affects its attractiveness as an export processing location we find that the upstream and downstream spatial linkages both have a strong and independent explanatory power we also explore what factors explain the influence of these spatial linkages

a review of the stern review on the economics of climate change how much and how fast should we react to the threat of global warming the stern review argues that the damages from climate change are large and that nations should undertake sharp and immediate reductions in greenhouse gas emissions an examination of the review s radical revision of the economics of climate change finds however that it depends decisively on the assumption of a near zero time discount rate combined with a specific utility function the review s unambiguous conclusions about the need for extreme immediate action will not survive the substitution of assumptions that are consistent with today s marketplace real interest rates and savings rates

attitudes toward catastrophe in light of climate change and other global threats policy commentators sometimes urge that society should be more concerned about catastrophes this paper reflects on what society s attitude toward low probability high impact events is or should be we first argue that catastrophe risk can be conceived of as a spread in the distribution of losses based on this conception we review studies from decision sciences psychology and behavioral economics that explore people s attitudes toward various social risks contray to popular belief we find more evidence against than in favor of catastrophe aversion the preference for a mean preserving contraction of the loss distribution and discuss a number of possible behavioral explanations next we turn to social choice theory and examine how various social welfare functions handle catastrophe risk we explain why catastrophe aversion may be in conflict with equity concerns and other regarding preferences finally we discuss current approaches to evaluate and regulate catastrophe risk

disaster on the horizon the price effect of sea level rise abstract homes exposed to sea level rise slr sell for approximately 7 less than observably equivalent unexposed properties equidistant from the beach this discount has grown over time and is driven by sophisticated buyers and communities worried about global warming consistent with causal identification of long horizon slr costs we find no relation between slr exposure and rental rates and a 4 discount among properties not projected to be flooded for almost a century our findings contribute to the literature on the pricing of long run risky cash flows and provide insights for optimal climate change policy

on modeling and interpreting the economics of catastrophic climate change with climate change as prototype example this paper analyzes the implications of structural uncertainty for the economics of low probability high impact catastrophes even when updated by bayesian learning uncertain structural parameters induce a critical tail fattening of posterior predictive distributions such fattened tails have strong im plications for situations like climate change where a catastrophe is theoretically possible because prior knowledge cannot place sufficiently narrow bounds on overall damages this paper shows that the economic consequences of fat tailed structural uncertainty along with unsureness about high temperature damages can readily outweigh the effects of discounting in climate change policy analysis