indenture an institution for a credible commitment without extortion abstract the aim of kritikos and bolle kritikos a s bolle f journal of economic behavior and organization 34 1998 279 294 was to analyze the institution of the indenture game within today s institutional setting unfortunately holt bases his rejoinder on a historical occurrence with a different institutional context this explains why his rejoinder is inconsistent

strategic buyers and exclusionary contracts this paper characterizes equilibrium exclusionary contracts between buyers an incumbent firm and a potential entrant when buyers can either vertically integrate or contract with the outside entrant in this setting exclusionary contracts are generally shown to be efficient and to deter inefficient entry that would otherwise occur with multiple unorganized buyers equilibrium contracts are shown to take a divide and conquer form and in some cases to deter some efficient entry in such cases efficient contracting can be restored by a policy that prohibits price discrimination and gives agents free reign to sign exclusionary agreements copyright 1994 by american economic association

indenture a viable contract for a sequential one shot prisoners dilemma a reply to holt abstract holt s argument is wrong a closer look at the structure of the game and at the equilibrium selection criterion shows that mutual co operation is secured in an indenture game

scientific ambiguity and climate policy economic evaluation of climate policy traditionally treats uncertainty by appealing to expected utility theory yet our knowledge of the impacts of climate policy may not be of sufficient quality to be described by unique probabilistic beliefs in such circumstances it has been argued that the axioms of expected utility theory may not be the correct standard of rationality by contrast several axiomatic frameworks have recently been proposed that account for ambiguous knowledge in this paper we apply static and dynamic versions of a smooth ambiguity model to climate mitigation policy we obtain a general result on the comparative statics of optimal abatement and ambiguity aversion and then extend our analysis to a more realistic dynamic setting where we introduce scientific ambiguity into the well known dice model of the climate economy system for policy relevant exogenous mitigation policies we show that the value of emissions abatement increases as ambiguity aversion increases and that this ambiguity premium can in some plausible cases be very large in these cases the effect of ambiguity aversion on welfare is comparable to that of other much studied welfare parameters thus ambiguity aversion may be an important neglected aspect of climate change economics and seems likely to provide another argument for strong abatement policy

contracts as a barrier to entry it is shown that an incumbent seller who faces a threat of entry into his or her market will sign long term contracts that prevent the entry of some lower cost producers even though they do not preclude entry completely moreover when a seller possesses superior information about the likelihood of entry it is shown that the length of the contract may act as a signal of the true probability of entry

active learning and optimal climate policy this paper develops a climate economy model with uncertainty irreversibility and active learning whereas previous papers assume learning from one observation per period or experiment with control variables to gain additional information this paper considers active learning from investment in monitoring specifically in improved observations of the global mean temperature we find that the decision maker invests a significant amount of money in climate research far more than the current level in order to increase the rate of learning about climate change this helps the decision maker make improved decisions the level of uncertainty decreases more rapidly in the active learning model than in the passive learning model with only temperature observations as the uncertainty about climate change is smaller active learning reduces the optimal carbon tax the greater the risk the larger is the effect of learning the method proposed here is applicable to any dynamic control problem where the quality of monitoring is a choice variable for instance the precision at which we observe gdp unemployment or the quality of education

environmental regulation with technology adoption learning and strategic behavior we analyze a model of environmental regulation with learning about environmental damages and endogenous choice of emissions abatement technology by a polluting firm we compare environmental policy under discretion in which policy is updated upon learning new information versus under rules in which policy is not updated when investment in abatement technology is made prior to the resolution of uncertainty neither discretion nor rules with either taxes or standards achieve an efficient solution except in special cases when there is little uncertainty rules are superior to discretion because discretionary policy gives the firm an incentive to distort investment in order to influence future regulation however when uncertainty is large discretion is superior to rules because it allows regulation to incorporate new information taxes are superior to standards under discretion regardless of the relative slopes of marginal costs and marginal damages for the case of quadratic abatement costs and damages

adjustment costs from environmental change abstract the paper is concerned with the case whereby the distribution of a firm s productivity shocks changes without the knowledge of the firm over time the firm learns about the nature and extent of the change in the distribution of the shock and adjusts incurring adjustment costs in the process the long run loss in profits due to the shift in the distribution we term the equilibrium response the transitory loss in profits incurred while the firm is learning about the distribution shift is termed the adjustment cost the theory is then applied to the problem of measuring adjustment costs in the face of imperfectly observed climate change in agriculture the empirical part of the paper involves estimating a restricted profit function for agricultural land in a five state region of the midwest us as a function of prices land characteristics actual weather realizations and expected weather we then simulate the effect of an unobserved climate shock where learning about the climate shock is by observing the weather and updating prior knowledge using bayes rule we find adjustment costs to climate change are 1 4 of annual land rents

belief based refinements in signalling games abstract there are many economic problems which when modelled as games of incomplete information give rise to many sequential equilibria severely limiting the usefulness of the model there has recently been a large literature devoted to refining the set of equilibria in order to reduce this multiplicity by restricting the set of admissible disequilibrium beliefs this paper argues that the logical foundations of some refinements and the equilibria they focus on are problematic and further proposes an alternative refinement that avoids the difficulties we also provide an existence theorem covering a broad class of signalling games often studied in economics journal of economic literature classification numbers c72 c70 d82

climate change policy what do the models tell us very little a plethora of integrated assessment models iams have been constructed and used to estimate the social cost of carbon scc and evaluate alternative abatement policies these models have crucial flaws that make them close to useless as tools for policy analysis certain inputs e g the discount rate are arbitrary but have huge effects on the scc estimates the models produce the models descriptions of the impact of climate change are completely ad hoc with no theoretical or empirical foundation and the models can tell us nothing about the most important driver of the scc the possibility of a catastrophic climate outcome iam based analyses of climate policy create a perception of knowledge and precision but that perception is illusory and misleading jel c51 q54 q58

growth dynamics and education spending the role of inherited tastes and abilities we present an overlapping generations model with endogenous growth in which children inherit human capital and standard of living aspirations from the previous generation adults evaluate their own consumption with respect to a baseline requirement which depends on their parents past consumption the interaction between these two intergenerational externalities leads to rich dynamics first starting with too high aspirations or with too low human capital will conduct the economy into a poverty trap second the growth rate and the savings rate are characterized by oscillations third a repelling cycle may delimit a basin of attraction around the balanced growth path this may lead countries starting with too high human capital to a boom followed by an irreversible decline c 2001 elsevier science b v all rights reserved

optimal learning on climate change why climate skeptics should reduce emissions climate skeptics typically argue that the possibility that global warming is exogenous implies that we should not take additional action towards reducing emissions until we know what drives warming this paper however shows that even climate skeptics have an incentive to reduce emissions such a directional change generates information on the causes of global warming since the optimal policy depends upon these causes they are valuable to know although increasing emissions would also generate information that option is inferior due its irreversibility we show that optimality can even imply that climate skeptics should actually argue for lower emissions than believers

precautionary principle and the optimal timing of environmental policy under ambiguity i consider a problem in environmental policy design in which i focus on stock pollutants in particular i consider stock pollutants that cause severe damage on the environment and do not depreciate at all once they are released into the atmosphere and the ocean the purposes of this paper are 1 to provide an economic foundation for environmental policies based on the precautionary principle and the 1992 rio declaration on environment and development and 2 to show that this optimal timing rule has a reservation property furthermore i analyze the effect of an increase in ambiguity on the optimal timing of adopting some environmental policy and show that an increase in ambiguity decreases the optimal timing of adopting the environmental policy

risk aversion and adaptive management insights from a multi armed bandit model of invasive species risk this article explores adaptive management am for decision making under environmental uncertainty in the context of targeting invasive species inspections of agricultural imports i find that risk aversion increases the relative value of am and can increase the rate of exploratory action while calls for am in natural resource management are common many analyses have identified modest gains from this approach i analytically and numerically examine the distribution of outcomes from am under risk neutrality and risk aversion the inspection decision is framed as a multi armed bandit problem and solved using the lagrangian decomposition method results show that even when expected gains are modest asymmetry in the distribution of outcomes has important implications notably am can serve to buffer against large losses even if the most likely outcome is a small loss

on environmental kuznets curves arising from stock externalities abstract we develop a stock externality model in an optimal growth framework and examine the relationship between economic growth and the environment we find that as incomes rise over the growth path both the marginal benefits of pollution control and the marginal costs of pollution control rise if at a given income level the marginal benefits rise more than the marginal costs the emissions income relationship has a negative slope at that income level and vice versa we are thus able to generate examples of emissions income relationships of varying shapes by varying pollution specific parameters which determine marginal costs and benefits such as the convexity of the cost function the rate of decay of the stock of pollution and the share of consumption in the composite good an inverted u shape relationship an environmental kuznets curve requires only minimal assumptions a convex cost function and that environmental quality is a normal good imply an inverted u shape relationship for an open set of parameters we also examine how environment income relationship varies according to what measure is used for the environment emissions stock of pollution or emissions control

actively learning about demand and the dynamics of price adjustment by observing the quantity demanded at particular prices a firm may learn about the parameters of its demand curve in such an environment price changes obstruct the learning process by inducing additional noise the authors paper constructs a dynamic model where a price setting firm endogenously controls the speed of learning the model provides a possible explanation for price inertia as a stable pricing policy allows the firm to learn more rapidly which improves future expected profits furthermore even in the long run learning continues to affect the firm s optimal price copyright 1990 by royal economic society

optimal timing problems in environmental economics abstract because of the uncertainties and irreversibilities that are often inherent in environmental degradation its prevention and its economic consequences environmental policy design can involve important problems of timing i use a simple two period model to illustrate these optimal timing problems and their implications for environmental policy i then lay out and solve a continuous time model of policy adoption in which the policy itself entails sunk costs and environmental damage is irreversible the model generalizes earlier work in that it includes two stochastic state variables one captures uncertainty over environmental change and the other captures uncertainty over the social costs of environmental damage solutions of the model are used to show the implications of these two types of uncertainty for the timing of policy adoption

exclusionary vertical contracts and product market competition this article considers whether a monopolist is able to deter more efficient entrants through contracting with buyers in the antitrust literature the chicago school s stand is that such contracts cannot be anticompetitive hence vertical contracts should be accorded per se legal status in a four stage game with the following features 1 the incumbent enjoys a first mover advantage 2 the entrant must incur some sunk cost to enter the market and 3 entry is uncertain the author shows that vertical contracts can be anticompetitive if there exists product market competition thus the author advocates caution in treating all contracts as per se legal a three factor repeated measures experiment tested the effect of leadership style charismatic structuring and considerate on performance improvement on a manufacturing task over four trials findings from a repeated measures multivariate analysis of variance indicated that individual exposed to considerate leadership had superior initial performance but that this difference faded over time further analysis indicated that self efficacy fully mediated the relationship between leadership style and performance copyright 1999 by university of chicago press

large scale scenario analysis of future low carbon energy options abstract in this study we use a multi model framework to examine a set of possible future energy scenarios resulting from rd and portfolios lacking ccs and nuclear tend to be stochastically dominated by others we find that the dominance of ccs becomes even stronger as uncertainty in climate damages increases finally we show that there is significant value in carefully choosing a portfolio as relatively small portfolios can dominate large portfolios

energy prices and carbon taxes under uncertainty about global warming this paper extends the strategic interactions between producers of fossil fuels concerned about their profits and a taxing government concerned about the consumers welfare for uncertainty global warming follows an ito process stochasticity requires to differentiate between reversible and irreversible emissions in contrast to the deterministic version the unconstrained reversible case allows for a closed form solution but not the more realistic and constrained case nevertheless interesting analytical properties e g about when to stop emissions implicit conservation due to monopolistic supply are derived and complemented by a numerical example

a simple state contingent pricing rule for complex intertemporal externalities abstract some externalities such as global warming involve complex relationships between emissions and an environmental state variable with effects over lags of uncertain length coming up with theoretically motivated and practical policy options in such cases has proven difficult deterministic intertemporal general equilibrium models yield what appear to be feasible optimal price paths but only by assuming away many key uncertainties nor do they specify how the possibility of new information should affect the policy path bayesian models allow limited uncertainty and optimal learning based on observed effects of policy changes but suggest a discouraging delay before optimal policy can be identified a full insurance model suggests that risk aversion and fat tailed probabilities of catastrophe imply an implausibly or at least impractically large risk premium implying that practical policy decisions depend so critically on uncertain parameters as to be unavoidably arbitrary this paper proposes an entirely new approach based on the observation that the situation giving rise to a complex intertemporal externality also yields an observable state variable that contains information relevant to the identification of the optimal policy path i derive a simple transformation by which the state variable can yield a good approximation to the optimal externality price i outline assumptions sufficient to yield the transformation and present numerical examples that illustrate its ability to follow linear and nonlinear first best price paths a specific application to greenhouse gases is proposed

expectation calculation and macroeconomic dynamics the authors establish a framework wherein agents make expectation revision decisions subject to a specified calculation technology and preferences over forecast errors the technology endows agents with correctly specified economic models but the cost of expectation calculation using these models leads to gradual and incomplete adjustment to long run rational expectation equilibrium the rational expectations hypothesis emerges as a special case of the equilibrium paths obtained in the authors framework in a natural rate model of monetary policy calculation technology gives rise to long run nonneutrality and hysteresis effects and incomplete adjustment of forecast rules causes output fluctuations to be amplified copyright 1992 by american economic association

regulation with anticipated learning about environmental damages a regulator anticipates learning about the relation between environmental stocks and economic damages for a model with linear quadratic abatement costs and environmental damages and a general learning process we show analytically that anticipated learning decreases the optimal level of abatement at a given information set if learning causes the regulator to eventually decide that damages are higher than previously thought learning eventually increases abatement learning also favors the use of taxes rather than quotas using a model that is calibrated to describe the problem of global warming we show numerically that anticipated learning causes a significant reduction in first period abatement and a small increase in the preference for taxes rather than quotas even if the regulator s initial priors about environmental damages are much too optimistic he is able to learn quickly enough to keep the expected stock trajectory near the optimal trajectory

hostages as a commitment device a game theoretic model and an empirical test of some scenarios abstract hostage posting is a mechanism of cooperation in social and economic relations with incentive problems a game theoretic model of hostage posting as a commitment device is presented cooperation via hostage posting is individually rational if it is supported by a subgame perfect equilibrium maximin properties of such equilibria are also considered predictions derived from the model were tested in several experiments results support the empirical significance of subgame perfect equilibria and of maximin strategies the institution of hostages is an ancient technique that deserves to be studied by game theory as does the practice of drinking wine from the same glass or of holding gang meetings in places so public that neither side could escape if it subjected the other to massacre schelling 1960 p 135

naked exclusion efficient breach and downstream competition previous papers by eric b rasmusen j mark ramseyer and john s wiley jr 1991 and ilya r segal and michael d whinston 2000 argue that exclusive contracts can inefficiently deter entry in the presence of scale economies and multiple buyers we first show that these results no longer hold when buyers are final consumers who can breach these contracts and pay expectation damages we then show however that exclusive contracts can inefficiently deter entry if buyers are downstream competitors even in the absence of scale economies and even if breach is possible

exclusive quality exclusive quality in the case of vertically differentiated products bertrand competition at the retail level does not prevent an incumbent upstream firm from using exclusivity contracts to deter the entry of a high quality rival indeed because of differentiation the incumbent s inferior product is not eliminated upon entry due to the resulting competitive pressure a retailer who considers rejecting the exclusivity contract expects to earn much less than the incumbent s monopoly rents thus in equilibrium the incumbent can always offer high enough an upfront payment to induce all retailers to sign the contract and achieve exclusion this is true under linear pricing for intermediate levels of entry costs and with two part tariffs even in the absence of entry costs copyright 2010 the author the journal of industrial economics 2010 blackwell publishing ltd and the editorial board of the journal of industrial economics

group purchasing nonlinear tariffs and oligopoly abstract loyalty discounts are nonlinear tariffs that condition rebates or marginal prices on meeting aggregate purchase or market share targets these discounts are widespread and are often the impetus for consumers to form buying groups or group purchase organizations gpos this paper models the competitive effects of the introduction of a gpo into a market within which the preferences of the gpo s members are horizontally differentiated while nonlinear tariffs are an effective way for a monopolist to extract consumer surplus when two suppliers compete using such schedules the results are far more competitive in comparison to simple bertrand nash competition with linear tariffs this result holds when the product of each of the suppliers is attractive to a substantial portion of consumers in our model the nonlinear schedule puts all customers in play to a degree that contrasts sharply with the competition at the margin characteristic of constant per unit prices moreover competing in nonlinear tariffs removes allocative inefficiency that can result from single price competition

exclusive dealing and entry when buyers compete rasmusen et al 1991 and segal and whinston 2000 show that an incumbent monopolist might prevent entry of a more efficient competitor by exploiting externalities among buyers we show that their results hold only when downstream competition among buyers is weak under fierce downstream competition if entry took place a free buyer would become more competitive and increase its output and profits at the expense of buyers that sign an exclusive deal with the incumbent anticipating that orders from a single buyer would trigger entry no buyer will sign the exclusive deal and entry will occur this result is robust across different specifications of the game jel k21 l12 l42

learning and stock effects in environmental regulation the case of greenhouse gas emissions abstract this paper concerns the optimal regulation of greenhouse gases that lead to global climate change in particular we focus on uncertainty and learning which over time resolves uncertainty we present an empirical stochastic model of climate economy interactions and present results on the tension between postponing control until more is known vs acting now before irreversible climate change takes place uncertainty in our model is in the damage caused by global warming the results suggest that a temporary carbon tax may dominate a permanent one because a temporary tax may induce increased flexibility

commitment versus discretion in climate and energy policy to decarbonize the power sector policy makers need to commit to long term credible rules for climate and energy policy otherwise risk of opportunistic policy making will impair investments into low carbon technologies however the future benefits and costs of decarbonization are subject to substantial uncertainties thus there may also be societal gains from allowing policy makers the discretion to adjust the policies as new information becomes available we examine how this trade off between policy commitment either unconditional or state contingent and discretion affects the optimal intertemporal design of market based instruments in the power sector using a dynamic partial equilibrium model we show that commitment to a state contingent level of ambition for the market based instrument leads to higher welfare than both unconditional commitment and discretion with benefit uncertainty the choice between the practically more feasible approaches of unconditional commitment and discretion is analytically ambiguous a basic numerical illustration suggests that policy discretion may outperform unconditional commitment in terms of welfare however this result is reversed when only a limited fraction of benefit uncertainty resolves in reasonable time when future policy makers have own agendas or when investors are risk averse with cost uncertainty policy discretion is welfare superior if the government can commit to a technology deployment target

learning and climate feedbacks optimal climate insurance and fat tails we study the effect of potentially severe climate change on optimal climate change policy accounting for learning and uncertainty in the climate system in particular we test how fat upper tailed uncertainty over the temperature change from a doubling of greenhouse gases the climate sensitivity affects economic growth and emissions policy in addition we examine whether and how fast uncertainties could be diminished through bayesian learning our results indicate that while overall learning is slow the mass of the fat tail diminishes quickly since observations near the mean provide evidence against fat tails we denote as partial learning the case where the planner rejects high values of the climate sensitivity with high confidence even though significant uncertainty remains fat tailed uncertainty without learning reduces current emissions by 38 relative to certainty indicating significant climate insurance or paying to limit emissions today to reduce the risk of very high temperature changes is optimal however learning reduces climate insurance by about 50 the optimal abatement policy is strongly influenced by the current state of knowledge even though greenhouse gas ghg emissions are difficult to reverse non fat tailed uncertainty is largely irrelevant for optimal emissions policy

naked exclusion an experimental study of contracts with externalities this paper reports the results of an experiment designed to assess the ability of an incumbent seller to profitably foreclose a market with exclusive contracts we use the strategic environment described by rasmusen ramseyer and wiley 1991 and segal and whinston 2000 where entry is unprofitable when sufficiently many downstream buyers sign exclusive contracts with the incumbent when discrimination is impossible the game resembles a stag hunt coordination game in which the buyers payoffs are endogenously chosen by the incumbent seller exclusion occurs when the buyers fail to coordinate on their preferred equilibrium two way non binding pre play communication among the buyers lowers the power of exclusive contracts and induces more generous contract terms from the seller when discrimination and communication are possible the exclusion rate rises divide and conquer strategies are observed more frequently when buyers can communicate with each other exclusion rates are significantly higher when the buyers payoffs are endogenously chosen rather than exogenously given finally secret offers are shown to decrease the incumbent s power to profitably exclude

exclusive contracts and demand foreclosure a firm may induce some customers to sign exclusive contracts in order to deprive a rival of the minimum viable size exclude it from the market and enjoy increased market power this strategy may result in socially inefficient exclusion even if the excluded firm is present at the contracting stage and can make counteroffers in addition allowing for breach penalty clauses decreases firms incentives to exclude rivals because such clauses allow a firm to use customers as a conduit for the transfer of another firm s profits

indenturing banknotes as a mechanism to induce cooperation in conflict games abstract a principal wants an agent to do something for him but does not want to pay him the agent wants to get the money but does not want to work for it how can the socially efficient result of working and paying be achieved if no enforceable contract can be concluded and the game is played only once a class of one shot games indenture games is analyzed where efficient behaviour is the unique stable equilibrium

combining price and quantity controls to mitigate global climate change abstract uncertainty about compliance costs causes otherwise equivalent price and quantity controls to behave differently and leads to divergent welfare consequences although most of the debate on global climate change policy has focused on quantity controls due to their political appeal this paper argues that price controls are more efficient simulations based on a stochastic computable general equilibrium model indicate that the expected welfare gain from the optimal price policy is five times higher than the expected gain from the optimal quantity policy an alternative hybrid policy combines both the political appeal of quantity controls with the efficiency of prices using an initial distribution of tradeable permits to set a quantitative target but allowing additional permits to be purchased at a fixed trigger price even sub optimal hybrid policies offer dramatic efficiency improvements over otherwise standard quantity controls for example a 50 trigger price per ton of carbon converts the 3 trillion expected loss associated with a simple 1990 emission target to a 150 billion gain these results suggest that a hybrid policy is an attractive alternative to either a pure price or quantity system

would hotelling kill the electric car in this paper we show that the potential for endogenous technological change in alternative energy sources may alter the behaviour of resource owning firms when technological progress in an alternative energy source can occur through learning by doing resource owners face competing incentives to extract rents from the resource and to prevent expansion of the new technology we show that in such a context it is not necessarily the case that scarcity driven higher traditional energy prices over time will induce alternative energy supply as resources are exhausted rather we show that as we increase the learning potential in the substitute technology lower equilibrium energy prices prevail and there may be increased resource extraction and greenhouse gas emissions we show that the effectiveness and the incidence of emissions reduction policies may be altered by increased potential for technological change our results suggest that treating finite resource rents as endogenous consequences of both technological progress and policy changes will be important for the accurate assessment of climate change policy

naked exclusion with minimum share requirements we consider a class of contracts in which buyers commit to giving a seller some minimum share of their total purchases we show that such contracts can be used by an incumbent seller to reduce the probability of entry by a rival seller when the incumbent can commit to its selling price as part of the contract we further show that such contracts can be profitable for the incumbent even when exclusive dealing would not be and even when buyers can coordinate their accept or reject decisions the average price paid by the buyers will be higher and welfare will be lower whether or not the incumbent s exclusionary conduct turns out to be successful in preventing entry

exclusive dealing and entry when buyers compete comment in this paper fm s equilibrium analysis is shown to contain some errors fixing these errors changes their conclusions for some of the cases they consider exclusive deals written between an incumbent and competitive downstream buyers will still often arise in equilibrium thereby block ing efficient entry inefficient exclusion arises to protect industry profits from competition the issue centers on how competition works when upstream firms sell to consumers through two com peting downstream buyers in the case upstream firms can offer downstream buyers two part tariffs the analysis of competition in this setting turns out to be surprisingly subtle and the analysis here should be of more general interest to those modeling competition in vertical settings the particular model fm consider is based on the cost specification in segal and whinston 2000 sect iv in which the incumbent faces a potential entrant that has a lower cost of production but faces some fixed cost of entry two identical downstream buyers compete in prices for final consum ers exclusive deals involve the incumbent offering buyers a fixed compensation for agreeing not to purchase from the entrant fm derive their results under two different assumptions on wholesale pricing upstream firms are required to set linear wholesale prices section i and upstream firms are allowed to offer two part tariff contracts section ii since restricting upstream firms to charge linear wholesale prices to buyers seems inconsistent with assuming the incumbent can offer exclu sive contracts with a fixed compensation in the initial stage and since linear wholesale prices can lead to double marginalization problems the focus in this paper is on the less restrictive case consid ered by fm where upstream firms are allowed to offer downstream buyers two part tariffs 1 in this setting correcting fm s analysis shows that entry arises only when scale economies are not too important and the entrant s efficiency advantage is sufficiently large when either

rejoinder to kritikos and bolle making indenture viable the extortionary power of pre commitment in iterated prisoner s dilemma abstract kritikos and bolle s approach is still flawed but a viable indenture game can still readily be structured within the context of iterated prisoner s dilemma

carbon prices for the next hundred years this paper examines the socially optimal pricing of carbon emissions over time when climate change impacts are unknown potentially high consequence events the carbon price tends to increase with income but learning about impacts or their absence decouples the carbon price from income growth the price should grow faster than the economy if the past warming is not substantial enough for learning the true long run social cost it grows slower than the economy as soon as the warming generates information about events that could have arrived but have not done so a quantitative assessment shows that the price grows roughly at the rate of the economy for the next 100 years

optimal taxes on fossil fuel in general equilibrium we analyze a dynamic stochastic general equilibrium dsge model with an externality through climate change from using fossil energy our central result is a simple formula for the marginal externality damage of emissions or equivalently for the optimal carbon tax this formula which holds under quite plausible assumptions reveals that the damage is proportional to current gdp with the proportion depending only on three factors i discounting ii the expected damage elasticity how many percent of the output flow is lost from an extra unit of carbon in the atmosphere and iii the structure of carbon depreciation in the atmosphere thus the stochastic values of future output consumption and the atmospheric co2 concentration as well as the paths of technology whether endogenous or exogenous and population and so on all disappear from the formula we find that the optimal tax should be a bit higher than the median or most well known estimates in the literature we also formulate a parsimonious yet comprehensive and easily solved model allowing us to compute the optimal and market paths for the use of different sources of energy and the corresponding climate change we find coal rather than oil to be the main threat to economic welfare largely due to its abundance we also find that the costs of inaction are particularly sensitive to the assumptions regarding the substitutability of different energy sources and technological progress

a 4 stated dice quantitatively addressing uncertainty effects in climate change we introduce a version of the dice 2007 model designed for uncertainty analysis dice is a wide spread deterministic integrated assessment model of climate change climate change long term economic development and their interactions are highly uncertain the quantitative analysis of optimal mitigation policy under uncertainty requires a recursive dynamic programming implementation of integrated assessment models such implementations are subject to the curse of dimensionality every increase in the dimension of the state space is paid for by a combination of exponentially increasing processor time lower quality of the value or policy function approximations and reductions of the uncertainty domain the paper promotes a state reduced recursive dynamic programming implementation of the dice 2007 model we achieve the reduction by simplifying the carbon cycle and the temperature delay equations we compare our model s performance and that of the dice model to the scientific aogcm models emulated by magicc 6 0 and find that our simplified model performs equally well as the original dice model our implementation solves the infinite planning horizon problem in an arbitrary time step the paper is the first to carefully analyze the quality of the value function approximation using two different types of basis functions and systematically varying the dimension of the basis we present the closed form continuous time approximation to the exogenous discretely and inductively defined processes in dice and we present a numerically more efficient re normalized bellman equation that in addition can disentangle risk attitude from the propensity to smooth consumption over time

regime shifts and management regime shifts are substantial reorganizations in system structure functions and feedbacks which can lead to changes in the provision of ecosystem services with significant impacts on human well being recent research has documented cases of regime shifts in local and regional systems and there is mounting concern about regime shifts of global significance in this paper we discuss management of social ecological systems in light of the potential for regime shift management that increases system resilience and lowers the probability of regime shifts is beneficial when regime shifts are likely to reduce human well being it may not always be possible to avoid harmful regime shifts so building capacity to adapt should a regime shift occur is beneficial too adaptive management can help reduce uncertainty about the likelihood of regime shifts how this likelihood can be affected by management action and the impact of regime shifts on well being linking scientific understanding with decision making is important but distributional consequences can impede decision making and action

experimentation with accumulation abstract we study signal dependent experimentation in the presence of accumulation and show that the passive learner s action surprisingly coincides with the experimentor s when the unknown term is the one determining the decay rate of the stock while they differ when the parameter being learned is the one measuring the accumulation rate these results highlight the importance of the dynamic structure of the problem in signal dependent experimentation moreover they have important consequences for the pollution accumulation debate currently in progress

naked exclusion comment the ability of an incumbent firm to deter entry by writing exclusionary contracts with customers has been a subject of contention in the antitrust literature the courts concern with such exclusionary contracts has been challenged by those who argue that an incumbent faced with buyers whose interest is to promote entry and competition would have to pay buyers more for the inclusion of exclusionary provisions than it could possibly gain from exclusion in a provocative article eric b rasmusen et al 1991 henceforth rrw have argued that an incumbent may in fact be able to exclude rivals profitably using such contractual provisions because it can exploit buyers lack of coordination in essence if buyers expect other buyers to sign such provisions then they may see little reason not to do so themselves the rrw argument is potentially an important one because most alleged instances of entry deterrence through exclusionary contracts with customers occur in situations with multiple buyers unfortunately however rrw s two main results contain errors in this note we reconsider the rrw model providing correct characterizations of the likelihood and cost of exclusion for an incumbent firm our results indicate that while the intuition suggested by rrw is valid the equilibrium likelihood and cost of exclusion differ from what rrw derive moreover our analysis illuminates some further aspects of exclusionary contracting with multiple buyers among these issues we focus on how an incumbent can use discriminatory offers to exploit the externalities that exist among buyers in the provision of competition in section i we review the basic assumptions of the rrw model in sections ii and iii we then consider in turn the cases of simultaneous and sequential offers studied by rrw for the simultaneous model we distinguish between settings in which the incumbent can and cannot discriminate in its offers to different buyers this distinction is the source of the problem in rrw s analysis their simultaneous offer model assumes no discrimination but the proof of their proposition 2 assumes at times that discrimination is feasible we show that absent the ability to discriminate the incumbent can exclude profitably only when buyers fail to coordinate on their most preferred continuation equilibrium in contrast we show that when discrimination is possible the incumbent need not rely on a lack of buyer coordination to segal department of economics landau building stanford university stanford ca 94305 e mail ilya segal stanford edu whinston department of economics northwestern university 2003 sheridan road evanston il 60208 e mail mwhinston nwu edu we thank eric rasmusen john wiley and participants in the berkeley stanford iofest the university of copenhagen vertical restraints conference and a seminar at the antitrust division of the u s department of justice for helpful comments we thank federico echenique for excellent research assistance 1 for example a recent department of justice investigation concerned the use of exclusive contracts by the leading provider of computerized ticketing services ticketmaster most major cities have several large concert sports venues in many cities ticketmaster has exclusive contracts with a very large share of these venues 2 the other leading response to the argument that contracts with buyers cannot be a profitable method of exclusion is given in philippe aghion and patrick bolton 1987 section i one factor limiting the applicability of the aghion and bolton theory however is that it involves partial exclusion the contracts signed are not fully exclusionary they involve finite stipulated damages and the profitability of the strategy arises from extracting rents from an entrant when entry occurs indeed in the aghion and bolton model contracts that fully exclude offer no benefits over writing no contract at all in section iii of their paper aghion and bolton also discuss a two buyer version of their model in which externalities arise across buyers in contrast to the analysis here and in rrw they allow the incumbent to make an offer to a buyer i that is conditional on the acceptance decision of the other buyer 3 r innes and r j sexton 1994 also discuss the use of discriminatory offers in the context of a model in which buyers can form coalitions with the entrant

malthus and climate change betting on a stable population abstract a standard assumption in integrated assessment models of climate change is that population and productivity are growing but at a decreasing rate we explore the significance of the assumption of population and productivity growth for greenhouse gas abatement after all there has been no long run slowdown in the growth of productivity over the past few centuries and the rate of population growth has actually been increasing for the past 19 centuries even if either of these growth rates were expected to slow by how much is subject to great uncertainty we show computationally that such continued growth greatly increases the severity of climate change indeed we find that climate change is a problem in large part caused by exogenous population and productivity growth rapid reductions in growth make climate change a small problem smaller reductions in growth imply climate change is a very serious problem indeed analogously reductions in the growth rate of population can be effective in controlling climate change

repeated games played by overlapping generations of players the present paper tries to explain cooperative behaviour in an organization run by a sequence of long but finitely lived agents we show that the folk theorem holds for infinitely repeated games with overlapping generations of finitely lived players any mutually beneficial outcome can approximately be sustained if the player s life span and the overlapping periods are long enough the result is stronger than the usual folk theorems in that it employs no assumption on the stage game such as the full dimensionality of payoff set or multiplicity of equilibria

communicating trade offs amid controversial science decision support for climate policy abstract the paper considers the decision that arises in climate policy where there is expert disagreement about the correct scientific model and where a group of stakeholders needs to agree on a common policy target policy choice is posed as a decision under knightian uncertainty where decision makers lack grounds for assigning a particular probability distribution across contending forecasting models the decision is then framed as one of balancing two competing objectives that plausibly align with the dominant concern of stakeholders from each side in the policy debate a decision criterion is proposed to identify options for compromise that balance these objectives in different ways the criterion spans three standard non bayesian decision criteria policies generated by the criterion are combined with visual tools to communicate what s at stake in an environmental policy decision in which stakeholders disagree both about scientific models and about the relative importance of risks to the environment versus risks to economic growth the approach summarizes information that could be useful to policy makers tasked with negotiating a compromise the framework is applied to climate policy using dice 2007 nordhaus 2008 the results highlight a basic asymmetry between the mistake of doing too little and that of doing too much that suggests a strong argument for avoiding the current status quo of global inaction

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

information aggregation in a prediction market for climate outcomes abstract two forms of uncertainty in climate policy are the wide range of estimated marginal costs and uncertainty over credibility of rival information sources we show how a recently proposed solution to the first problem also helps address the second the policy is an emissions tax tied to average temperatures coupled with permits that exempt the emitter from paying the tax in a future year it has been shown that the resulting tax path will be correlated with future marginal damages it has been conjectured that the permit prices will yield unbiased forecasts of the climate which if true would address the second uncertainty we confirm the conjecture by describing a trading mechanism that converges on unbiased forecasts if traders are risk neutral risk aversion slows down but does not prevent convergence we also show that the forecasts are more likely to be sufficient statistics the stronger the consensus on climate science

the nobel memorial prize for william d nordhaus william d nordhaus and paul m romer received the 2018 sveriges riksbank prize in economic sciences in memory of alfred nobel this paper surveys nordhaus contributions on integrating climate change into long run macroeconomic analysis for which he was recognized with this prize

bayesian learning growth and pollution abstract environmental problems such as climate change have great uncertainties current expectations are that uncertainties about climate change will be resolved quickly we examine this hypothesis theoretically and computationally we consider bayesian learning about the relationship between greenhouse gas levels and global mean temperature changes a key uncertainty learning is non trivial because of a stochastic shock to the realized temperature we find theoretically the expected learning time which is related to the variance of the shock and the emissions policy implying a tradeoff between the benefits of controlling emissions and information we imbed the learning model into an optimal growth model with a climate sector and solve the resulting dynamic program we find computationally that learning takes on average over 90 yr far longer than currently believed

policy experimentation political competition and heterogeneous beliefs abstract we consider a two period model in which an incumbent political party chooses the level of a current policy variable unilaterally but faces competition from a political opponent in the future both parties care about voters payoffs but they have different beliefs about how policy choices will map into future economic outcomes we show that when the incumbent party can endogenously influence whether learning occurs through its policy choices policy experimentation future political competition gives it a new incentive to distort its policies it manipulates them so as to reduce uncertainty and disagreement in the future thus avoiding facing competitive elections with an opponent very different from itself the model thus demonstrates that all incumbents can find it optimal to over experiment relative to a counterfactual in which they are sure to be in power in both periods we thus identify an incentive for strategic policy manipulation that does not depend on parties having conflicting objectives but rather stems from their differing beliefs about the consequences of their actions

an experimental study of exclusive contracts abstract this paper reports results from a laboratory experiment based on exclusive contracts that may theoretically lead to inefficient naked exclusion of a potential rival the data indicate that changes in the number of buyers in the market have no significant effect on exclusion rates but the likelihood of inefficient exclusion is decreased both when a larger fraction of signed buyers are needed to deter a rival s entry and when buyers engage in non binding communication these results have antitrust implications both in terms of helping to identify at risk market characteristics and suggesting potential competition enhancing strategies a sub game of the experiment where buyers make signing decisions can be illustrated as a coordination game with the unique feature that payoffs are affected by a separate but interested party the incumbent seller i find that the height of the potential function and relevant basin of attraction especially when combined with quantal response estimation have larger predictive power in this sub game than several other equilibrium selection criteria

optimal climate change mitigation under long term growth uncertainty stochastic integrated assessment and analytic findings abstract economic growth over the coming centuries is one of the major determinants of today s optimal greenhouse gas mitigation policy at the same time long run economic growth is highly uncertain this paper is the first to evaluate optimal mitigation policy under long term growth uncertainty in a stochastic integrated assessment model of climate change the sign and magnitude of the impact depend on preference characteristics and on how damages scale with production we explain the different mechanisms driving optimal mitigation under certain growth under uncertain technological progress in the discounted expected utility model and under uncertain technological progress in a more comprehensive asset pricing model based on epstein zin weil preferences in the latter framework the dominating uncertainty impact has the opposite sign of a deterministic growth impact the sign switch results from an endogenous pessimism weighting all of our numeric scenarios use a dice based assessment model and find a higher optimal carbon tax than the deterministic dice base case calibration

the climate change learning curve abstract the purpose of this paper is to confront economic models of climate change with the reality that limited information exists with which to form expectations about the evolution of the climate a key element in the tension between those who believe we should impose aggressive climate change mitigation policies and those who do not is the question of if we are merely in a long period of shock induced above average temperatures or if observed increases in temperature are a result of carbon emissions this paper characterizes learning dynamics resulting from the use of observations of temperature to update beliefs about two key characteristics of global climate the persistence of natural trends and the sensitivity of temperature to atmospheric carbon levels this paper shows that contrary to predictions in the literature that uncertainty may be resolved very quickly the time to learn the true processes may be in the order of thousands of years further this paper shows the effects of uncertainty on the likelihood that observations from the statistical record lead to important estimate and policy errors

global warming and a potential tipping point in the atlantic thermohaline circulation the role of risk aversion the risk of catastrophes is one of the greatest threats of climate change yet conventional assumptions shared by many integrated assessment models such as dice lead to the counterintuitive result that higher concern about climate change risks does not lead to stronger near term abatement efforts this paper examines whether this result still holds in a refined dice model that employs the epstein zin utility specification and that is fully coupled with a dynamic tipping point model describing the evolution of the atlantic thermohaline circulation thc risk is captured by the possibility of a future collapse of the circulation and it is nourished by fat tailed uncertainty about climate sensitivity this uncertainty is assumed to resolve in the middle of the second half of this century and the near term abatement efforts which are undertaken before that point of time can be adjusted afterwards these modelling choices allow posing the question of whether aversion to this specific tipping point risk has a significant effect on near term policy efforts the simulations however provide evidence that it has little effect for the more likely climate sensitivity values a collapse of the circulation would occur in the more distant future in this case acting after learning can prevent the catastrophe implying the remarkable insensitivity of the near term policy to risk aversion for the rather unlikely and high climate sensitivity values the expected damage costs are not great enough to justify taking very costly measures to safeguard the thc our simulations also provide some indication that risk aversion might have some effect on near term policy if inertia limiting the speed of decarbonisation is accounted for as it is highly uncertain how restrictive this kind of inertia will be future research might investigate the effects of risk aversion if additional uncertainty about inertia is considered

naked exclusion in the lab the case of sequential contracting in the context of the naked exclusion model of rasmusen ramseyer and wiley 1991 and segal and whinston 2000b we examine whether sequential contracting is more conducive to exclusion in the lab and whether it leads to lower exclusion costs for the incumbent than simultaneous contracting we find that an incumbent who proposes exclusive contracts to buyers sequentially is better able to deter entry than an incumbent who proposes contracts simultaneously in contrast to theory this comes at a substantial cost for the incumbent

exclusive contracts and market dominance we propose a new theory of exclusive dealing the theory is based on the assumption that a dominant firm has a competitive advantage over its rivals and that the buyers willingness to pay for the product is private information in this setting the dominant firm can impose contractual restrictions on buyers without necessarily compensating them implying that exclusive dealing contracts can be both profitable and anticompetitive we discuss the general implications of the theory for competition policy and illustrate by examples its applicability to antitrust cases jel d21 d43 d82 d86 k21 l13 l40