automate the identification of technical patterns a k nearest neighbour model approach to explore profitable patterns in historical stock prices ordinarily a promising pattern is selected by rule of thumb and then its performance is verified by comparing the conditional return of t

energy and physical capital a case of non classical dynamics we study the importance of considering different energy requirements for physical capital and final good production in an overlapping generations olg resource economy in contrast to the standard olg framework but consistently with the empirical evidence we assume that the accumulation of physical capital requires more energy than the production of consumption goods focusing on exhaustible energy resources we find that olg equilibria can exhibit non classical dynamics the economy generates complex dynamics where differing from the response predicted by the standard approach resource prices may not increase monotonically this result illustrates that the technological assumptions behind the energy inputs should be taken with caution in particular on dynamic analyses involving exhaustible energy resources

modeling and forecasting electricity prices with input output hidden markov models in competitive electricity markets in addition to the uncertainty of exogenous variables such as energy demand water inflows and availability of generation units and fuel costs participants are faced with the uncertainty of their competitors behavior the analysis of electricity price time series reflects a switching nature related to discrete changes in competitors strategies which can be represented by a set of dynamic models sequenced together by a markov chain an input output hidden markov model iohmm is proposed for analyzing and forecasting electricity spot prices the model provides both good predictions in terms of accuracy as well as dynamic information about the market in this way different market states are identified and characterized by their more relevant explanatory variables moreover a conditional probability transition matrix governs the probabilities of remaining in the same state or changing to another whenever a new market session is opened the model has been successfully applied to real clearing prices in the spanish electricity market

pollution private investment in healthcare and environmental policy in this paper we demonstrate that in a two period overlapping generations model the relationship between environmental taxation and economic activity output level and growth has an inverted u shape when we take into account the detrimental impact of pollution on health and the individual decision of each working age agent to improve her health we also demonstrate that the link between environmental tax and lifetime welfare also has an inverted u shape and that a tighter environmental policy might enhance economic activity while reducing steady state lifetime welfare finally we investigate the social optimum and the determinants of the optimal environmental tax

environmental tax policy and intergenerational distribution abstract we study the effects of environmental taxation within the context of an overlapping generations model the quality of the environment is modelled as a durable consumption good introduction of the environmental tax harms old existing generations and benefits young existing generations as well as all future generations increasing the tax in a pareto improving manner is easier the higher the pre existing tax the reverse holds if tax policy is decided by majority rule a suitably designed bond policy can be used to redistribute the efficiency gains due to the internalisation of environmental externalities across the generations

the political economy of environmental taxes with an aging population this paper develops a two period overlapping generations model with environmental externalities and uncertain lifetimes and studies how two sources of population aging greater longevity and a lower rate of population growth affect the politically determined environmental tax and the quality of the environment it is shown that greater longevity and a lower rate of population growth have entirely different effects on these factors greater longevity has no effect on the environmental tax and has a non positive effect on the environmental quality whereas a lower rate of population growth has a negative effect on the tax and has a positive effect on the quality in addition the political decision making on the tax leads to an inefficient allocation of capital and environmental quality

an overlapping generations model with exhaustible resources and stock pollution this paper analyzes the nexus between resource exhaustion and pollution externality using an overlapping generations framework where each generation lives only for a finite period for a finite horizon model with production where there are many agents per generation the pareto inefficiency arises due to lack of intragenerational coordination and is propagated across generations the tax rates necessary for correcting this externality are characterized we also derive a modified hotelling rule according to which the equilibrium resource price rises slower than the rate of interest in order to account for the damages due to the pollution stock generated by the resource used for the case where the externality induced damage acts on production rather than the utility function pareto inefficiency is shown to persist even when there is intragenerational coordination

environmental valuation under sustainable development environmentalism has evolved since the 1960 s from a concern with the preservation of wilderness in the american experience to a concern over pollution of human habitat throughout the industrialized world northern anxiety spread to the loss of tropical rainforests and biodiversity in the south where environmentalism evolved further in an encounter with indigenous interpretations conditions and priorities by the late 1980 s climate change emerged as a central issue in a now global discourse on the relationship between environment and development the principle of sustainable development that current needs are to be met as fully as possible while ensuring that the life opportunities of future generations are undiminished relative to present is now widely accepted this paper illustrates that incorporating environmental values per se in decision making will not bring about sustainability unless each generation is committed to transferring to the next sufficient natural resources and capital assets to make development sustainable 11 refs 3 figs

renewable resource use and nonseparable amenity benefits we incorporate amenity benefits into an overlapping generations model with a renewable resource as a factor of production source of amenity benefits and store of value unlike the conventional renewable resource problems studied under the assumption of additive consumption and amenity benefits we let amenity benefits affect the utility of consumers in a nonseparable fashion we examine the role that weights given to consumption and amenities have for harvesting and the resource stock we characterize dynamics and stability of steady state equilibria with a logistic resource growth function we demonstrate in parametric and numerical models that the weights given to consumption and amenities in the utility function matter substantially for the steady state equilibrium stock and its stability and dynamics both conventional saddle point equilibria and indeterminacy with infinite number of equilibria and saddle node bifurcation is possible depending on the weights given to consumption and amenities in addition we show that for each inefficient equilibrium stock there is a unique subsidy rate that can move the economy from an inefficient equilibrium to an efficient one the presence of indeterminacy provides a challenge to resource policies because the system becomes unpredictable therefore expectations and market psychology may play an important role in resource utilization and provision of amenities

day ahead electricity price forecasting using the wavelet transform and arima models this paper proposes a novel technique to forecast day ahead electricity prices based on the wavelet transform and arima models the historical and usually ill behaved price series is decomposed using the wavelet transform in a set of better behaved constitutive series then the future values of these constitutive series are forecast using properly fitted arima models in turn the arima forecasts allow through the inverse wavelet transform reconstructing the future behavior of the price series and therefore to forecast prices results from the electricity market of mainland spain in year 2002 are reported

jointly produced exhaustible resources abstract natural resources are often produced jointly from composite ores which in turn are extracted from fixed reserve endowments in this paper market behavior is examined for such resources and it is shown how the price of each resource will depend on its demand and the demands and storage costs for the other resources present in the ore the measurement of resource scarcity is discussed and the effects of uncertainty over future resource demands are examined it is shown that the competitive market will still extract produce and store at socially optimal rates if firms are risk neutral and the average cost of storage is constant policy implications are noted particularly with reference to government stockpiling programs

on the intergenerational allocation of natural resources it is known hartwick and others that under standard assumptions a society that invests in reproducible capital the competitive rents on its current extraction of exhaustible resources will enjoy a consumption stream constant in time it is shown here that this result can be interpreted as saying that an appropriately defined stock of capital including the initial endowment of resources is being maintained intact and that consumption can be interpreted as the interest on that patrimony this seems like a useful rule of thumb for policy

the political economy of environmental policy with overlapping generations a two sector overlapping generations model illuminates the intergenerational effects of a tax that protects an environmental stock a traded asset capitalizes the economic returns to future tax induced environmental improvements benefiting the current asset owners the old generation absent a transfer the tax harms the young generation by decreasing their real wage future generations benefit from the tax induced improvement in environmental stock the principal intergenerational conflict arising from the tax is between generations alive at the time society imposes the policy not between generations alive at different times a pareto improving tax can be implemented under various political economy settings

the optimal production of an exhaustible resource when price is exogenous and stochastic this paper examines the optimal production of a resource such as oil when its price is determined exogenously e g by a cartel such as opec and is subject to stochastic fluctuations away from an expected growth path we first examine the dependence of production on extraction cost and show that the conventional exponential decline curve is indeed optimal if marginal cost is constant with respect to the rate of extraction but is a hyperbolic function of the reserve level we next show that uncertainty about future price affects the optimal production rate in two ways first if marginal cost is a convex concave function of the rate of production stochastic fluctuations in price raise lower average cost over time so that there is an incentive to speed up slow down production second the option value of the reserve i e the ability to withhold production indefinitely and never incur the cost of extraction provides an incentive to slow down the rate of production

intergenerational competitive equilibria under technological uncertainty and an exhaustible resource constraint abstract this paper presents a model of competitive intertemporal equilibrium in a finite horizon overlapping generations economy facing technological uncertainty and an exhaustible resource constraint individuals form rational expectations regarding future prices and economic conditions and income is redistributed from one generation to the next through government mandated lump sum transfers under uncertainty the relationship between resource price appreciation and the interest rate is mediated by consumers risk aversion with respect to consumption in alternative states of nature the intuitively appealing proposition that the expected resource price rises at the expected rate of interest holds only as a special case if future generations are taken to be state contingent in the sense that their composition depends on the states of nature prevailing when they are born then equilibria are generally pareto efficient but if future generations are state independent so that the set of individuals born at a given date is independent of the prevailing state of nature then equilibria may be inefficient because markets do not exist where successive generations may equilibrate their marginal rates of substitution across consumption in alternative contingent states such inefficiencies may be remedied through the implementation of appropriate intergenerational transfers an optimal intergenerational welfare distribution may be supported as a competitive equilibrium if the income transfer regime is properly selected and enforced the social optima that result for a simple version of the model under the maximin welfare criterion indicate that greater sacrifices are required on the part of the present generation when future generations are taken to be state contingent than when they are regarded as state independent this finding provides a possible explanation for the extreme risk aversion of conservationists with respect to the welfare of future generations

is aging harmful to the environment how does aging affect the environment we analyze this question using anoverlapping generations model featuring uncertain lifetimes andenvironmental externalities we show that whether aging is harmful to theenvironment depends on the curvature of utility function which ismeasured by the degree of relative risk aversion we also explore theimplication of the results for environmental policy in an aging society

component estimation for electricity prices procedures and comparisons abstract electricity price time series usually exhibit some form of nonstationarity corresponding to long term behavior one or more periodic components as well as dependence on calendar effects as a result modeling electricity prices requires accounting for both long term and periodic components in the literature several filtering procedures have been proposed but a standard has not yet been found furthermore since different procedures are applied in contexts that are not homogeneous with respect to data periods and final goals a fair comparison is difficult this work considers several methods for component estimation in a homogeneous framework and compares them according to specific criteria the final purpose is to find an estimation procedure that performs well independently of the intended market and that can be proposed as a reference for electricity price time series filtering

a technique for estimating the discount rate in pindyck s stochastic model of nonrenewable resource extraction abstract the purpose underpinning this paper is to develop an empirically verifiable model of the economic behavior of a single competitive firm operating to exploit a single deposit of oil using pindyck s methodology this model is derived using a continuous time framework and stochastic optimal control the main contribution of the research lies in making the connection between dynamic economic modeling and statistical methods that arise naturally from stochastic optimization

a garch forecasting model to predict day ahead electricity prices price forecasting is becoming increasingly relevant to producers and consumers in the new competitive electric power markets both for spot markets and long term contracts price forecasts are necessary to develop bidding strategies or negotiation skills in order to maximize profits this paper provides an approach to predict next day electricity prices based on the generalized autoregressive conditional heteroskedastic garch methodology that is already being used to analyze time series data in general a detailed explanation of garch models is presented and empirical results from the mainland spain and california deregulated electricity markets are discussed

competitive equilibria and sustainable growth in a life cycle model with natural resources the purpose of this note is to consider interactions between capital accumulation and natural resource exploitation in diamond s 1965 overlapping generations olg model the presumption in the literature on economic growth under resource constraints e g solow 1974 or stiglitz 1974 is that constant standards of living are possible in the presence of nonreproducible natural resources even in the absence of technical progress provided only that capital and resources are good substitutes in production and society makes sufficient investments in reproducible capital to offset the optimally declining stock of natural resources this literature ignores generation overlap and treats society in each period as a single generation which cares about and also discounts the welfare of its immediate descendants and which has complete control over the rate of resource use and the saving rate whether a sequence of selfish finite lived and interdependent generations interacting via competitive markets will implement these paths is an open question this note introduces a stationary population log linear version of diamond s model in which natural resources are selfreproducible and essential in production and capital depreciates completely after one period in this environment it is technically feasible to achieve growth paths in which the input and the stock of natural resources are constant and in which capital accumulation leads to growth in living standards these paths of resource use can be interpreted as emanating from the normative concept of sustainable development now advocated

arima models to predict next day electricity prices price forecasting is becoming increasingly relevant to producers and consumers in the new competitive electric power markets both for spot markets and long term contracts price forecasts are necessary to develop bidding strategies or negotiation skills in order to maximize benefit this paper provides a method to predict next day electricity prices based on the arima methodology arima techniques are used to analyze time series and in the past have been mainly used for load forecasting due to their accuracy and mathematical soundness a detailed explanation of the aforementioned arima models and results from mainland spain and californian markets are presented

reducing electricity price forecasting error using seasonality and higher order crossing information commodity prices are volatile and their volatility changes over time electricity prices are even more volatile in general because customers cannot easily switch to other energy source when the electricity prices fluctuate electricity prices also have strong seasonal behavior because the demand of electricity depends on the season to address these characteristics a time series forecasting model with seasonality and higher order crossing information for electricity prices is proposed the model measures the similarity between two time series by using their higher order crossing information the model can predict not only day ahead prices short term forecasting but also a series of prices for one week ahead or even longer simultaneously medium term price curve forecasting the model is tested on both high and low volatile data sets to evaluate its robustness and generality it is also shown that the model can produce more accurate prediction than some well known models

renewable resources in an overlapping generations economy without capital abstract we incorporate a renewable resource into an overlapping generations model without capital and with quasi linear preferences besides being an input for production the resource serves as a store of value we characterize the dynamics efficiency and stability of the steady state equilibria the stability properties are sensitive to the type of resource growth for constant growth there is only one steady state equilibrium which is stable and efficient in the general case of the concave growth function there are usually at least two steady state equilibria one of which is stable and the other one unstable the unstable steady state is efficient but the stable one may or may not be we study the robustness of our results by assuming a logarithmic utility function we show that for the cobb douglas production function the steady state is unique and stable regardless of whether the equilibrium is efficient or inefficient our analytical results are illustrated by numerical calculations

democracy and environmental quality we develop and estimate an econometric model of the relationship between several local and global air pollutants and economic development while allowing for critical aspects of the socio political economic regime of a state we obtain empirical support for our hypothesis that democracy and its associated freedoms provide the conduit through which agents can exercise their preferences for environmental quality more effectively than under an autocratic regime thus leading to decreased concentrations or emissions of pollution however additional factors such as income inequality age distribution education and urbanization may mitigate or exacerbate the net effect of the type of political regime on pollution depending on the underlying societal preferences and the weights assigned to those preferences by the state

electricity market price forecasting based on weighted nearest neighbors techniques this paper presents a simple technique to forecast next day electricity market prices based on the weighted nearest neighbors methodology first it is explained how the relevant parameters defining the adopted model are obtained such parameters have to do with the window length of the time series and with the number of neighbors chosen for the prediction then results corresponding to the spanish electricity market during 2002 are presented and discussed finally the performance of the proposed method is compared with that of recently published techniques

classification of future electricity market prices forecasting short term electricity market prices has been the focus of several studies in recent years although various approaches have been examined achieving sufficiently low forecasting errors has not been always possible however certain applications such as demand side management do not require exact values for future prices but utilize specific price thresholds as the basis for making short term scheduling decisions in this paper classification of future electricity market prices with respect to pre specified price thresholds is introduced two alternative models based on support vector machines are proposed in a multi class multi step ahead price classification context numerical results are provided for classifying prices in ontario s and alberta s markets

an overlapping generations model of climate economy interactions a numerically calibrated overlapping generations model of climate change and the world economy is examined in this paper in the absence of intergenerational transfers efficient rates of greenhouse gas emissions abatement rise from 16 in the present to 25 in the long run while mean global temperature increases by 7 40c relative to the preindustrial norm a utilitarian optimum which attaches equal weight to each generation s life cycle utility yields abatement rates that rise from 48 to 89 with a long run temperature increase of 3 40c a second best utilitarian path in which intergenerational transfers are by assumption institutionally infeasible also supports stringent abatement measures i introduction the infinitely lived agent framework pioneered by frank ramsey 1928 has emerged as a central structure in the economics of climate change as characterized by ipcc 1996 working group iii climate change occurs when anthropogenic emissions of greenhouse gases principally carbon dioxide but also chlorofluorocarbons methane nitrous oxide and water vapor contribute to long term increases in mean global temperature potentially disrupting ecological systems and climate dependent production activities the best known study on the economics of this subject is nordhaus 1994 dynamic model of climate and the economy dice which incorporates assumptions regarding the costs and benefits of greenhouse gas emissions in a standard one sector growth model in nordhaus analysis a 50 reduction in greenhouse gas emissions would reduce gross world output by 0 93 a doubling of greenhouse gas concentrations relative to the preindustrial norm which is expected to occur by the middle of the twenty first century would reduce output by

incentive equilibrium in an overlapping generations environmental game we consider two overlapping generations that want to coordinate their strategies of working consuming and controlling pollution since the cooperative solution is not an equilibrium and hence is not a self enforcing contract a mechanism is required to sustain it we show how incentive strategies and the resulting incentive equilibrium could provide such a mechanism we also derive the conditions that ensure the credibility of these strategies

electricity price curve modeling and forecasting by manifold learning this paper proposes a novel nonparametric approach for the modeling and analysis of electricity price curves by applying the manifold learning methodology locally linear embedding lle the prediction method based on manifold learning and reconstruction is employed to make short term and medium term price forecasts our method not only performs accurately in forecasting one day ahead prices but also has a great advantage in predicting one week ahead and one month ahead prices over other methods the forecast accuracy is demonstrated by numerical results using historical price data taken from the eastern u s electric power markets

forecasting next day electricity prices by time series models in the framework of competitive electricity markets power producers and consumers need accurate price forecasting tools price forecasts embody crucial information for producers and consumers when planning bidding strategies in order to maximize their benefits and utilities respectively this paper provides two highly accurate yet efficient price forecasting tools based on time series analysis dynamic regression and transfer function models these techniques are explained and checked against each other results and discussions from real world case studies based on the electricity markets of mainland spain and california are presented

life expectancy and the environment we present an olg model in which life expectancy and environmental quality dynamics are jointly determined agents may invest in environmental care depending on how much they expect to live in turn environmental conditions affect life expectancy as a result our model produces a positive correlation between longevity and environmental quality both in the long run and along the transition path eventually multiple equilibria may also arise some countries might be caught in a low life expectancy low environmental quality trap this outcome is consistent with stylized facts relating life expectancy and environmental performance measures we also discuss the welfare and policy implications of the inter generational externalities generated by individual choices finally we show that our results are robust to the introduction of growth dynamics based on physical or human capital accumulation c 2009 elsevier b v all rights reserved

energy price forecasting in the ontario competitive power system market this paper introduces a method for forecasting energy prices using artificial intelligence methods such as neural networks and fuzzy logic and a combination of the two the new approach is compared with some of the exiting methods various factors affecting the market clearing price are investigated results for the ontario electricity market are presented

intergenerational altruism and the environment we construct an overlapping generations model of pollution externality in which individuals are altruistically linked to their offspring as in barro 1974 it is shown that steady state consumption may be a decreasing function of the intergenerational degree of altruism despite individuals altruism the competitive equilibrium is not optimal we thus study the social optimum and show that it can be decentralized

conservationist government policies and intergenerational equity in an overlapping generations model with renewable resources abstract this paper shows that in overlapping generations models incorporating renewable natural resources competition may lead to perpetually declining living standards in environments in which it is technically feasible to achieve intergenerationally equitable distributions of consumption first and second best conservationist government policies are examined these include forced nationalization of the entire stock of natural capital government open market purchases and sales of natural capital taxation of industrial use of resources and subsidies to private investments in natural capital

electricity price short term forecasting using artificial neural networks this paper presents the system marginal price smp short term forecasting implementation using the artificial neural networks ann computing technique the described approach uses the three layered ann paradigm with backpropagation the retrospective smp real world data acquired from the deregulated victorian power system was used for training and testing the ann the results presented in this paper confirm considerable value of the ann based approach in forecasting the smp

energy clearing price prediction and confidence interval estimation with cascaded neural networks the energy market clearing prices mcps in deregulated power markets are volatile good mcp prediction and its confidence interval estimation will help utilities and independent power producers submit effective bids with low risks mcp prediction however is difficult since bidding strategies used by participants are complicated and various uncertainties interact in an intricate way furthermore mcp predictors usually have a cascaded structure as several key input factors need to be predicted first cascaded structures are widely used however they have not been adequately investigated this paper analyzes the uncertainties involved in a cascaded neural network nn structure for mcp prediction and develops the prediction distribution under the bayesian framework a computationally efficient algorithm to evaluate the confidence intervals by using the memoryless quasi newton method is also developed testing results on a classroom problem and on new england mcp prediction show that the method is computationally efficient and provides accurate prediction and confidence coverage the scheme is generic and can be applied to various networks such as multilayer perceptrons and radial basis function networks

an overlapping generations model of growth and the environment this article analyzes the potential conflict between economic growth and the maintenance of environmental quality in an overlapping generations model short lived individuals make decisions which have long lasting effects on both factor productivity and the environment the model provides a theoretical explanation of observed correlations between environmental quality and income whereby economic growth is associated first with declines then improvements in environmental quality it suggests circumstances in which multiple pareto ranked steady state equilibria may arise and in which sustained growth of both capital and environmental quality may occur overmaintenance of the environment analogous to dynamically inefficient overaccumulation of capital may emerge copyright 1994 by royal economic society

sustainability constraints versus optimality versus intertemporal concern and axioms versus data sustainable sustained or survivable development are defined here as distinct sustainability constraints on intertemporal distribution in a context which ignores uncertainty environmental and intratemporal concerns such constraints are neither self contradictory nor redundant for they can conflict with maximizing the present value of utility optimality nor inferior since the axioms underlying optimality are ethically arbitrary and refuted by empirical psychological data axiomatic arguments may clarify but cannot resolve debates about intertemporal concerns data suggest that sustainability constraints are not respected and that intertemporal welfare functions containing a preference for sustained improvement may better reflect what bodies politic mean by sustainability

intergenerational resource rights efficiency and social optimality the discipline of economics is generally defined as the science of the allocation of scarce resources between competing social objectives given an initial distribution of resources between economic agents how would they behave so as to improve their welfare according to the pareto criterion the agents would exchange commodities until the opportunities for fruitful exchange were fully exhausted and no agent could be made better off without rendering at least one other agent worse off pareto efficiency is a powerful concept in microeconomic analysis provided that the initial distribution of property rights is equitable allocative efficiency gives rise to the best of all possible worlds acknowledging that the assumptions of perfect competition are often violated firms are monopolistic information is incomplete and externalities exist economists have argued for the modification of institutions so that economic reality will conform more closely to the assumptions of the model that yields such gratifying results but microeconomic theory has always maintained that allocative efficiency is in itself insufficient to maximize social welfare bator 1957 a social welfare function is required to discriminate a social optimum among the array of efficient allocations that correspond to alternative assignments of property rights though economists have posited alternative functional forms for the sake of pursuing conceptual arguments welfare functions have remained elusive constructs for well known theoretical and practical reasons consequently a sharp line of demarcation has been drawn between questions of efficiency the province of economics and equity the principal focus of ethical and political discourse in resource economics however the line demarcating efficiency and equity is often crossed the term optimal depletion appears regularly where only efficient depletion is meant while political debates about resource exploitation over time are laden with questions of the proper distribution of our natural patrimony between generations resource economists have predominantly espoused particular use rules that guarantee efficiency but overlook potential improvements in social welfare achievable through the reassignment of property rights across generations we document the evolution and current status of the misuse of the term optimal depletion in section ii we develop a simple two generation three period general equilibrium model in section iii to illustrate how alternative distributions of resource rights between generations relate to alternative pareto efficient solutions in section iv we demonstrate how different social welfare functions affect the optimal solution and associated assignment of resource rights between generations

day ahead price forecasting of electricity markets by mutual information technique and cascaded neuro evolutionary algorithm in a competitive electricity market price forecasts are important for market participants however electricity price is a complex signal due to its nonlinearity nonstationarity and time variant behavior in spite of much research in this area more accurate and robust price forecast methods are still required in this paper a combination of a feature selection technique and cascaded neuro evolutionary algorithm cnea is proposed for this purpose the feature selection method is an improved version of the mutual information mi technique the cnea is composed of cascaded forecasters where each forecaster consists of a neural network nn and an evolutionary algorithm ea an iterative search procedure is also incorporated in our solution strategy to fine tune the adjustable parameters of both the mi technique and cnea the price forecast accuracy of the proposed method is evaluated by means of real data from the pennsylvania new jersey maryland pjm and spanish electricity markets the method is also compared with some of the most recent price forecast techniques

sustainable forestry timber bequests future generations and optimal tax policy this paper analyzes harvesting and timber bequest behavior in a two period overlapping generations model where the government uses site productivity yield and inheritance taxation the ceteris paribus effects of forest and inheritance taxes are derived first then the paper discusses the optimal design of forest and inheritance taxes by assuming that intergenerational externalities are either absent or operative in the absence of intergenerational externalities it is optimal to use only the site productivity tax and not to introduce yield and inheritance taxes at all in the presence of intergenerational externalities the situation changes the paper demonstrates that the externality can be internalized by introducing either a yield tax or an inheritance subsidy or both if the government is able to use both at the same time it is desirable to use the yield tax to punish excessive harvesting and an inheritance subsidy to bribe to give bequests