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Abstract:
A model of ecologically sustainable endogenous growth is presented, in which environmental quality has a positive influence on individual welfare and on the productivity of capital. The effect of different environmental policies on the long-run growth of the economy is studied in the framework of this model. The results establish that an optimal policy which taxes production and subsidies pollution abatement has a favourable effect on environmental quality, and could increase the growth rate if the positive external effects of the environment on the productivity are important. Furthermore, it is shown that this kind of environmental policy is neutral in budgetary terms, i.e. tax receipts are equal to subsidies. Finally, it is demonstrated that a policy based on emission control will only have a positive effect on the growth rate if the initial level of environmental quality is sufficiently low.

Sustainable Growth, External Effects, Pigouvian Taxes, Emission Standards

Abstract:
In this paper the scope of the applicability of the Stackelberg equilibrium concept in differential games is investigated. Firstly, it is showed that for a class of differential games with state-interdependence the stationary feedback Nash equilibrium coincides with the stationary feedback Stackelberg equilibrium independently of the player being the leader of the game. Secondly, sufficient conditions for obtaining the coincidence between the two equilibria are defined. A review of different economic models shows that this coincidence is going to occur for a good number of economic applications of differential games. This result appears because of the continuous-time setting in which differential games are defined. In this setting the first movement advantage of the leader may disappears and then both equilibria coincide.

differential games, stationary feedback Nash equilibrium, stationary feedback Stackelberg equilibrium, coincidence

Abstract:
In this paper the stability of an International Environmental Agreement (IEA) among N identical countries that emit a pollutant are studied using a two-stage game. In the first stage each country decides noncooperatively whether or not to join an IEA, and in the second stage signatories jointly against nonsignatories determine their emissions in a dynamic setting defined in continuous time. For this second stage we have studied both the open-loop Nash equilibrium and the feedback Nash equilibrium. A numerical simulation shows that a bilateral coalition is the unique self-enforcing IEA independently of the gains coming from cooperation and the kind of strategies played by the agents (open-loop or feedback strategies). We have also studied the effects of a minimum participation clause finding that for this case a self-enforcing IEA just consists of the number of countries established in the clause. The rationale for the low level of international cooperation that can be expected for controlling pollution is given by the fact that nonsignatories benefit from the emissions control supported by signatories because of the public bad nature of the pollution stock. The result is that signatories always do better by withdrawing from the agreement whenever the number of signatories is higher than two.

International Environmental Agreements, stock externalities, differential games, open-loop Nash equilibrium, feedback Nash equilibrium, linear strategies

Abstract:
Much of the literature on international environmental agreements uses static models, although most important transboundary pollution problems involve stock pollutants. The few papers that study IEAs using models of stock pollutants do not allow for the possibility that membership of the IEA may change endogenously over time. In this paper we analyse a simple infinite-horizon version of the Barrett (1994) model, in which unit damage costs increase with the stock of pollution, and countries decide each period whether to join an IEA. We show that there exists a steady-state stock of pollution with corresponding steady-state IEA membership, and that if the initial stock of pollution is below (above) steady-state then membership of the IEA declines (rises) as the stock of pollution tends to steady-state. As we increase the parameter linking damage costs to the pollution stock, initial and steady-state membership decline; in the limit, membership is small and constant over time.

Self-enforcing international environmental agreements, Internal and external stability, Stock pollutant

Abstract:
In this paper the scope of Bergstrom's (1982) results is studied. Moreover, his analysis is extended assuming that extraction cost is directly related to accumulated extractions. For the case of a competitive market it is found that the optimal policy is a constant tariff if extraction is costless. However, with depletion effects, the optimal tariff must ultimately be decreasing. For the case of a monopolistic market the results depend crucially on the kind of strategies the importing country governments can play and on whether the monopolist chooses the price or extraction rate. For a price-setting monopolist it is shown that the importing countries cannot use a tariff to capture monopoly rents if they are constrained to use open-loop strategies, even if the governments sign a tariff agreement. This result is drastically modified if the importing countries in the tariff agreement use Markov (feedback) strategies. For a quantity-setting monopolist the nature of the game changes and the importing country governments find it advantageous to set a tariff on resource importations. Moreover, in this case the importing countries in a tariff agreement enjoy a strategic advantage which allows them to behave as a leader.

Tariffs, Tariff agreements, Non renewable resources, Depletion effects, Price-setting monopolist, Quantity-setting monopolist, Differential games, Open-loop strategies, Linear strategies, Markov-perfect Nash equilibrium, Markov-perfect Stackelberg equilibrium

Abstract:
In this paper we model the case of an international non-renewable resource monopolist as a dynamic game between a monopolist and n importing countries governments, and we investigate whether a tariff on resource imports can be advantageous for the consumers of the importing countries when the monopolist sets the price and the importing countries governments act in a non-cooperative way. We find that a tariff is advantageous for the consumers even when there is not commitment to the trade policy although the part of the rent that can be reaped by the importing countries decreases substantially with the number of importing countries. The optimality of the tariff in our dynamic game is explained by the fact that through the tariff the governments of the importing countries can influence the dynamics of the accumulated extractions and hence the extraction costs and the evolution of the monopolist price.

tariffs, non-renewable resources, depletion effects, price-setting monopolist, differential games, linear strategies, Markov-perfect Nash equilibrium

Abstract:
In this paper a two-stage game of international environmental agreement formation with asymmetric countries is solved. The equilibrium of the game allows to determine the number of countries interested in signing the agreement. Two cases are studied. In the first case, it is assumed that the only difference among countries is given by the abatement costs, and in the second case, by the environmental damages. In both cases, two different institutional settings, one without side payments and another with side payments, are considered. The results establish that the asymmetry assumption has no important effects on the scope of cooperation in comparison with the symmetric case if side payments are not used or the only difference among countries is given by the abatement costs. When the only difference are the environmental damages, the result is that the level of cooperation that can be bought through a self-financed side payment system increases with the degree of asymmetry.

Self-enforcing international environmental agreements, linear environmental damages, public bads

Abstract:
In this paper the optimal policy and the stability of a tariff agreement among the importers of a monopolized good that is sold in an integrated market are studied. To analyze the stability, the tariff agreement formation is modelled as a two-stage game. In the first stage each importer decides whether or not to sign the agreement and in the second stage the signatories and non-signatories choose their tariff whereas the monopoly chooses the quantity or the price. The findings show that the optimal policy of the importers depends on which strategic variable is selected by the monopolist but that, on the contrary, this decision has no effects on the level of cooperation that can be reached by a self-enforcing tariff agreement that, in any case, is very low.

Foreign monopolies, self-enforcing tariff agreements, integrated markets, tent-shifting hypothesis, prices versus quantities

Abstract:
Barrett's (1994) paper on transboundary pollution abatement shows that if the signatories of an international environmental agreement act in a Stackelberg fashion, then, depending on parameter values, a self-enforcing IEA can have any number of signatories between two and the grand coalition. Barrett obtains this result using numerical simulations in a pollution abatement model where he is not constraining emissions to be non-negative. Recent attempts to use analytical approaches and to explicitly recognize the non-negativity constraints have suggested that the number of signatories of a stable IEA may be very small. The way such papers have dealt with non-negativity constraints is to restrict parameter values to ensure interior solutions for emissions. We argue that a more appropriate approach is to use Kuhn-Tucker conditions to derive the equilibrium of the emissions game. When this is done we show, analytically, that the key results from Barrett's paper are maintained. Finally, we explain why his main conclusion is correct although his analysis can implicitly imply negative emissions.