cooperative management of groundwater resources in the presence of environmental externalities this paper investigates how cooperation among users can achieve a better management of groundwater in the presence of environmental externalities cooperation allows users to internalize the damages caused by their activities and reduce extractions the paper develops a game theoretical framework to assess the value of cooperation in an aquifer that is divided into three sub aquifers that are being overly exploited two types of externalities are modeled first water extractions in each sub aquifer impact water levels in neighboring sub aquifers extraction externality second the three sub aquifers are also connected to an ecosystem and thus decisions in each sub aquifer affect the health of the ecosystem environmental externality a cooperative game theory model is applied the model empirically shows how the uncontrolled extractions in each sub aquifer affects neighboring groundwater users but also cause severe impacts to the linked ecosystem the model is tested empirically in one of the most important aquifers in spain the eastern la mancha aquifer the results illustrate how both extraction and environmental externalities interact in affecting the likelihood of cooperation among the users the paper estimates the value of cooperation and its stability with and without the environmental externality

domestic taxation and international portfolio choice abstract given uncertain domestic currency denominated tax payments risk averse investors hold a portion of their wealth in a tax hedge portfolio which empirical results show is comprised chiefly of the domestic bond tax hedging may therefore explain the observed preference for home country assets

optimal currency risk hedging abstract this paper investigates the optimal hedging strategy of a domestic expected utility maximizer endowed with a temporarily non traded position in a foreign investment the domestic and foreign yield curves the exchange rate between the two involved currencies and the foreign investment value are stochastic and obey fairly general diffusion processes we compare the hedger s optimal strategies using either exchange rate forward contracts or futures contracts for both strategies the optimal number of contracts held can be broken down into several components having clear economic interpretations however while futures contracts are known in such a context to be more difficult to price than their forward counterparts the optimal strategy using them is simpler this is due to the fact that when forward contracts are used incurred profits or losses that accrue to the investor s wealth at each instant are locked in in the forward position up to the contract maturity thus discounting these gains or losses back at the current date brings about an interest rate risk therefore the investor s hedging strategy itself generates an additional risk which in turn induces the need for additional hedging the magnitude of the difference between the two hedge ratios may be significant under a set of plausible assumptions since in general financial markets are not complete the additional interest rate risk cannot be perfectly hedged hence the marking to market mechanism that characterizes futures contracts and allows for the complete elimination of this risk is valuable for risk averse agents

the minimum variance hedge ratio under stochastic interest rates in an environment where interest rates are stochastic we examine the case of a pure hedger endowed with a fixed position in a long term bond in contrast to conventional wisdom according to which the difference between hedging through forward contracts and futures is immaterial it turns out that the minimum variance hedge ratio using forwards comprises two terms instead of one only when using futures the magnitude of the difference between the two hedge ratios may be important under some plausible assumptions this result is due to the presence of additional interest rate risk that bears on the profit and loss statement associated with the forward position this sheds some additional light on the respective features of forward and futures contracts written on interest rate sensitive securities

valuation of the ecosystem services a psycho cultural perspective abstract valuation of ecosystems services has been a challenging issue for economists there is a growing concern to capture the total and incremental changes in services of different types of ecosystems mainly due to perturbations arising from anthropogenic activities market based valuation techniques have long been declared inadequate and a constructed market method such as the contingent valuation method albeit a robust tool does not seem to capture the expanse nuances and intricacies of many of the ecosystem services the paper attempts to address the lacunae in valuation of ecosystem services from a psychological perspective by arguing that the common person s perception of the ecosystem is quite different from what is conceptualized by conventional economists the paper shows how the ecological identity of individuals is revealed at various levels of the decision making hierarchy that is from local to regional and further onto a global level the paper builds upon insights from psychoanalytic psychology and environmental psychology further it outlines recent research findings from experimental psychology to redefine concepts such as ecological identity self other dichotomy and the fostering of identification with nature as issues that must be embraced in the valuation of ecosystem services extending the idea of relational goods and reciprocity the paper offers a deconstructed view of market forces and furthers the idea of interdisciplinary collaboration and cooperation in the valuation of ecosystem services in this perspective the dichotomy and schism between markets missing markets and non markets gets renovated and reconstructed beyond a utilitarian discourse

a note on merton s optimum consumption and portfolio rules in a continuous time model in the paper optimum consumption and portfolio rules in a continuous time model by r c merton j econ theory 3 1971 373 413 solutions obtained in cases when marginal utility at zero consumption is finite are not feasible while they do satisfy the hamilton jacobi bellman equations they do not represent appropriate value functions because the boundary behavior near zero wealth is not satisfactorily dealt with in this note we specify the boundary behavior and characterize optimal solutions journal of economic literature classification numbers 022 213

valuation of wetlands in a landscape and institutional perspective what is a wise use of nature this perennial issue always controversial due to conflicting human interests has in the last decade tended to be clothed in the context of sustainable development the rapid breakthrough of this concept in political and scientific spheres has brought to our attention the dependence of human survival and well being upon ecosystem supports e g baskin 1997 costanza et al 1997 daily 1997 as well as the susceptibility of ecosystems to human influences how can such a political and scientific attention to ecosystems be translated to good public policy one necessary prerequisite is likely to be the adoption of a landscape perspective such a perspective implies studies of the biological and physical interactions among a mosaic of ecosystems in heterogeneous land areas that together comprise landscapes it is worth emphasising however that human presence and man made social economic and physical structures are equally natural landscape elements continually interacting with ecosystems the fact that humans and nature are inseparable and the apparently ever increasing human influence on her biological and physical environments make an analysis of the linkages between ecosystems and humans an indispensable part of a landscape perspective institutional design in the context of interaction between society and nature has indeed been subject to several recent studies for example ostrom 1990 bromley 1991 hanna et al 1996 and berkes and folke 1998 institutions include social norms codes and other informal constraints for human behaviour as well as formal ones such as constitutions and laws their design is one key to understanding human preferences and behaviour in relation to nature the study of institutions is thus an integral part of a landscape perspective corresponding author tel 46 8 6739540 fax 46 8152464 e mail address tore beijer kva se t soderqvist

on the optimal hedge of a nontraded cash position in this paper we focus on the optimal demand for futures contracts by an investor with a logarithmic utility function who attempts to hedge a nontraded cash position when the analysis is conducted in the cash commodity price space we show that the value function associated with the bernoulli investor program is not additively separable thus suggesting that this investor hedges against shifts in the opportunity set as represented by the commodity price by establishing the equivalence between the cash formulation of the problem and the wealth formulation we are able to analyze the problem in the wealth commodity price space in this space we show the additive separability of the value function when the futures settlement price process is perfectly locally correlated with the commodity price process the demand for futures in this instance is composed of a a mean variance term and b a minimum variance component that is a classic feature of models with nontraded assets since the first best nonmyopic optimum is attained however the deviation from a mean variance demand should not be interpreted as the expression of a nonmyopic behavior but rather as an attempt to restore a first best optimum on the other hand when the correlation between the futures price and the underlying commodity price is imperfect in general the value function does not separate additively the first best solution cannot be attained and the optimal futures trading strategy involves a hedging term against shifts in the opportunity set in the classic dynamic portfolio problem the investor selects a trading strategy in risky and riskless assets so as to maximize his or her expected lifetime utility in this environment where all assets can be freely traded the logarithmic investor behaves myopically to the extent that he or she ignores shifts in the opportunity set when making current choices samuelson 271 mossin 24 hakansson 16 merton 22 in particular in models with continuous trading it turns out that the value function corresponding to the investor s program is additively separable in wealth and state variables the implication is that his or her behavior will be myopic i e that his or her demand functions for assets will be of the pure meanvariance efficiency type and in particular will not include any dynamic hedging components that are characteristic of financial markets with shifting opportunities in this paper we investigate the structure of the bernoulli investor s demand functions in the situation where one asset cannot be freely traded in the market

nontraded assets and the capm abstract asset pricing models that rely on the presence of non tradable assets such as human wealth to solve the equity premium puzzle have to confront the effect of decreasing absolute risk aversion rich investors who according to micro data hold the stock market and whose behavior is the one that matters at the margin for the determination of equilibrium asset prices are less risk averse ceteris paribus than the average consumer this paper highlights a channel through which the effect of decreasing absolute risk aversion can be overcome the existence of a positive correlation between the rates of return on traded assets and on the human capital of marginal investors

generalizing the permanent income hypothesis revisiting friedman s conjecture on consumption abstract friedman s contribution to the consumption literature goes well beyond the seminal permanent income hypothesis he conjectured that the marginal propensity to consume out of financial wealth shall be larger than out of human wealth the present discounted value of future labor income i present an explicitly solved model to deliver this widely noted consumption property by specifying that the conditional variance of changes in income increases with its level a larger realization of income not only implies a higher level of human wealth but also signals a riskier stream of future labor income inducing a higher precautionary saving and thus giving rise to friedman s conjecture appropriately adjusting human wealth for income risk i show that friedman s conjecture may be formulated as a generalized permanent income hypothesis i further show that friedman s conjecture captures the first order effect of stochastic precautionary savings finally i propose a natural decomposition of the optimal saving rule to formalize various motives for holding wealth as emphasized in friedman m 1957 a theory of the consumption function princeton university press princeton

equilibrium in securities markets with heterogeneous investors and unspanned income risk abstract in a finite time horizon incomplete market continuous time setting with dividends and investor incomes governed by arithmetic brownian motions we derive closed form solutions for the equilibrium risk free rate and stock price for an economy with finitely many heterogeneous cara investors and unspanned income risk in equilibrium the sharpe ratio is the same as in an otherwise identical complete market economy whereas the risk free rate is lower and consequently the stock price is higher the reduction in the risk free rate is highest when the more risk averse investors face the largest unspanned income risk

exchange rate variability and asset trade in popular discussion about the merits of different international monetary arrangements it is often maintained that increased exchange rate variability has a negative influence on international tra

optimal hedging and equilibrium in a dynamic futures market abstract this paper considers an agent maximizing the expected utility of the sum of the terminal value of a fixed portfolio of spot market assets and the terminal value of a margin account on a futures trading position closed form solutions for the optimal hedging strategy are provided in several special cases

optimal portfolio choice for long horizon investors with nontradable labor income this paper examines how risky labor income and retirement affect optimal portfolio choice with idiosyncratic labor income risk the optimal allocation to stocks is unambiguously larger for employed investors than for retired investors consistent with the typical recommendations of investment advisors increasing idiosyncratic labor income risk raises investors willingness to save and reduces their stock portfolio allocation towards the level of retired investors positive correlation between labor income and stock returns has a further negative effect and can actually reduce stockholdings below the level of retired investors financial advisors typically recommend that their customers invest more in stocks than in safe assets when they are working and to shift their investments towards safe assets when they retire jagannathan and kocherlakota 1996 malkiel 1996 by contrast the standard academic models of portfolio choice merton 1969 1971 samuelson 1969 show that retirement is irrelevant for portfolio decisions if investment opportunities are constant and human capital is tradable in this case the fraction of wealth optimally invested in risky assets should be constant over the lifetime of an individual recent research building on the pioneering work by merton 1971 shows that time varying investment opportunities result in portfolio rules with an intertemporal hedging component whose magnitude depends on the investment horizon of the investor kim and omberg 1996 balduzzi and lynch 1997 brennan schwartz and lagnado 1997 brandt 1999 campbell and viceira 1999 2001 barberis 2000 with time variation in investment opportunities retirement and death play an instrumental role as events that exogenously fix the individual s investment horizon more importantly retirement also marks the time at which individuals stop working and thereafter must live off their lifetime savings and possibly transfers from this perspective retirement matters for portfolio choice

valuing ecosystem services a shadow price for net primary production abstract we analyze the contribution of ecosystem services to gdp and use this contribution to calculate an empirical price for ecosystem services net primary production is used as a proxy for ecosystem services and along with capital and labor is used to estimate a cobb douglas production function from an international panel a positive output elasticity for net primary production probably measures both marketed and nonmarketed contributions of ecosystems services the production function is used to calculate the marginal product of net primary production which is the shadow price for ecosystem services the shadow price generally is greatest for developed nations which have larger technical scalars and use less net primary production per unit output the rate of technical substitution indicates that the quantity of capital needed to replace a unit of net primary production tends to increase with economic development and this rate of replacement may ultimately constrain economic growth

how firms should hedge substantial academic research explains why firms should hedge but little work has addressed how firms should hedge we assume that firms can experience costly states of nature and derive optimal hedging strategies using vanilla derivatives e g forwards and options and custom exotic derivative contracts for a value maximizing firm facing both hedgable price and unhedgable quantity risks customized exotic derivatives are typically better than vanilla contracts when correlations between prices and quantities are large in magnitude and when quantity risks are substantially greater than price risks finally we discuss how our model may be applied in practice copyright 2002 oxford university press

valuation by conflict abstract nonmarket valuation remains a central issue in ecological and environmental economics this paper examines the properties of an ex post revealed preference approach to value nonmarket goods valuation through observed effort expended in an environmental conflict we consider the strategic interaction between players in a conflict address the implied nash equilibrium and report a benchmark 4x rule as an ex post valuation estimate for a symmetric player conflict we then illustrate the degree of bias that exists once one allows for asymmetries in delegation ability and valuation the benchmark tends to overestimate value if a firm hires a powerful delegate who receives a large contingency fee

the rybczynski theorem in the three factor two good model abstract this paper proves that if each factor is normal in the three factor two good model the expansion of a factor endowment always increases at constant commodity prices the output of the commodity which uses the expending factor most intensively

ecosystem service value assessment for constructed wetlands a case study in hangzhou china abstract based on a comprehensive analysis of various classifications of natural resource values we summarized an ecological economic value system of constructed wetland cw ecosystems for treating eutrophic water using the cw located at the hangzhou botanical garden as an example the contingent valuation method cvm and shadow project approach spa were applied to estimate the economic values of cw system ecosystem services the cvm estimated a value of 800 000 yuan yuan chinese currency 7 6 yuan 1 usd as of august 2007 as the total economic value of the cw in a twenty year period meanwhile the spa calculated a value of 23 04 million yuan as the total economic value of the cw in a twenty year period it is determined that compared to the cvm the spa provides a more approximate value of the true monetary value of the hangzhou botanical garden cw this study could fill the gap of knowledge and provide a benchmark when evaluating constructed ecosystem services and help policy makers to promote the development of constructed wetlands in china

real options with constant relative risk aversion real options problems have recently attracted much attention worldwide one such problem is how to deal with claims on non traded assets often there is another traded asset which is correlated to the non traded asset and this traded asset is used as a proxy for hedging purposes we introduce a second non traded log brownian asset into the well known merton investment model with power law utility the investor has a claim on units of the non traded asset and the question is how to price and hedge this random payoff the presence of the second brownian motion means that we are in the situation of incomplete markets we propose an approximation to the solution for the optimal reservation price and hedge which is accurate when the position is small in comparison to wealth the resulting loss when a suboptimal proxy strategy is followed is shown to be approximately quadratic in 1

entrepreneurial finance and nondiversifiable risk w e develop a dynamic incomplete markets model of entrepreneurial firms and demonstrate the implications of nondiversifiable risks for entrepreneurs interdependent consumption portfolio allocation financing investment and business exit decisions we characterize the optimal capital structure via a generalized tradeoff model where risky debt provides significant diversification benefits nondiversifiable risks have several important implications more risk averse entrepreneurs default earlier but choose higher leverage lack of diversification causes entrepreneurial firms to underinvest relative to public firms and risky debt partially alleviates this problem and entrepreneurial risk aversion can overturn the risk shifting incentives induced by risky debt we also analytically characterize the idiosyncratic risk premium jel g11 g31 e20

an isomorphism between asset pricing models with and without linear habit formation we show an isomorphism between optimal portfolio selection or competitive equilibrium models with utilities incorporating linear habit formation and corresponding models without habit formation the isomorphism can be used to mechanically transform known solutions not involving habit formation to corresponding solutions with habit formation for example the constantinides 1990 and ingersoll 1992 solutions are mechanically obtained from the familiar merton solutions for the additive utility case without recourse to a bellman equation or first order conditions more generally recent solutions to portfolio selection problems with recursive utility and a stochastic investment opportunity set are readily transformed to novel solutions of corresponding problems with utility that combines recursivity with habit formation the methodology also applies in the context of hindy huang kreps 1992 preferences where our isomorphism shows that the solution obtained by hindy and huang 1993 can be mechanically transformed to dybvig s 1995 solution to the optimal consumption investment problem with consumption ratcheting this article presents a general method for solving asset pricing or portfolio selection models involving linear habit formation of the type studied by sundaresan 1989 constantinides 1990 detemple and zapatero 1991 ingersoll 1992 chapman 1998 and others the basic idea we pursue is that linear habit formation can be thought of as a redefinition of what constitutes consumption to include not only the current consumption rate but also a fictitious possibly negative consumption rate derived from past actual consumption by pricing out this fictitious consumption rate correctly the economy with linear habit formation can be mechanically transformed to an equivalent economy without habit formation this analysis simplifies and unifies existing results but also generates novel solutions for example together with the results of schroder and skiadas 1997 1999 our method produces optimal lifetime consumption and portfolio policies with preferences that combine recursive utility with habit formation under a stochastic

optimal consumption and equilibrium prices with portfolio constraints and stochastic income abstract this paper examines the intertemporal optimal consumption and investment problem in the presence of a stochastic endowment and constraints on the portfolio choices short sale and borrowing constraints as well as incomplete markets can be modeled as special cases of the class of constraints we consider existence of optimal policies is established under fairly general assumptions on the security price coefficients and the individual s utility function this result is obtained by using martingale techniques to reformulate the individual s dynamic optimization problem as an equivalent static one an explicit characterization of equilibrium risk premia in the presence of portfolio constraints is also provided in the unconstrained case this characterization reduces to consumption based capital asset pricing model journal of economic literatureclassification numbers g11 g12 c61 d52 d91

continuous time methods in finance a review and an assessment i survey and assess the development of continuous time methods in finance during the last 30 years the subperiod 1969 to 1980 saw a dizzying pace of development with seminal ideas in derivatives securities pricing term structure theory asset pricing and optimal consumption and portfolio choices during the period 1981 to 1999 the theory has been extended and modified to better explain empirical regularities in various subfields of finance this latter subperiod has seen significant progress in econometric theory computational and estimation methods to test and implement continuous time models capital market frictions and bargaining issues are being increasingly incorporated in continuous time theory the roots of modern continuous time methods in finance can be traced back to the seminal contributions of merton 1969 1971 1973b in the late 1960s and early 1970s merton 1969 pioneered the use of continuous time modeling in financial economics by formulating the intertemporal consumption and portfolio choice problem of an investor in a stochastic dynamic programming setting merton 1973b also showed how such a framework can be used to develop equilibrium asset pricing implications thereby significantly extending the asset pricing theory to richer dynamic settings and expanding the scope of applications of continuous time methods to study problems in financial economics 1 within a span of about 30 years from the publication of merton s inf luential papers continuous time methods have become an integral part of financial economics indeed in certain core areas in finance such as e g asset pricing derivatives valuation term structure theory and portfolio selection continuoustime methods have proved to be the most attractive way to conduct research and gain economic intuition the continuous time approach in these areas has produced models with a rich variety of testable implications the econometric theory for testing continuous time models has made rapid strides in the last decade and has thus kept pace with the impressive progress on the theoretical front one hopes that the actual empirical investigations and estimation using the new procedures will follow suit soon

an intertemporal general equilibrium model of asset prices this paper develops a continuous time general equilibrium model of a simple but complete economy and uses it to examine the behavior of asset prices in this model asset prices and their stochastic properties are determined endogenously one principal result is a partial differential equation which asset prices must satisfy the solution of this equation gives the equilibrium price of any asset in terms of the underlying real variables in the economy in this paper we develop a general equilibrium asset pricing model for use in applied research an important feature of the model is its integration of real and financial markets among other things the model endogenously determines the stochastic process followed by the equilibrium price of any financial asset and shows how this process depends on the underlying real variables the model is fully consistent with rational expectations and maximizing behavior on the part of all agents our framework is general enough to include many of the fundamental forces affecting asset markets yet it is tractable enough to be specialized easily to produce specific testable results furthermore the model can be extended in a number of straightforward ways consequently it is well suited to a wide variety of applications for example in a companion paper cox ingersoll and ross 7 we use the model to develop a theory of the term structure of interest rates many studies have been concerned with various aspects of asset pricing under uncertainty the most relevant to our work are the important papers on intertemporal asset pricing by merton 19 and lucas 16 working in a continuous time framework merton derives a relationship among the equilibrium expected rates of return on assets he shows that when investment opportunities are changing randomly over time this relationship will include effects which have no analogue in a static one period model lucas considers an economy with homogeneous individuals and a single consumption good which is produced by a number of processes the random output of these processes is exogenously determined and perishable assets are defined as claims to all or a part of the output of a process and the equilibrium determines the asset prices our theory draws on some elements of both of these papers like merton we formulate our model in continuous time and make full use of the analytical tractability that this affords the economic structure of our model is somewhat similar to that of lucas however we include both endogenous production and

saving and liquidity constraints this paper is concerned with the theory of saving when consumers are not permitted to borrow and with the ability of such a theory to account for some of the stylized facts of saving behavior the models presented in the paper seem to account for important aspects of reality that are not explained by traditional life cycle models copyright 1991 by the econometric society

valuing environmental resources under alternative management regimes abstract this paper shows that the economic values of resources depend in part on the management regime the value of a resource supporting a commercial fishery will depend on whether the fishery is optimally managed or open access the ellis fisher 1987 data are used to calculate values under alternative assumptions about management these calculations show that value is influenced not only by biological and economic factors but also by institutions

on the fluctuations in consumption and market returns in the presence of labor and human capital an equilibrium analysis abstract we examine the effects of human capital on consumption stock market and other fluctuations in a general equilibrium continuous time model a representative consumer worker investor derives utility from consumption and leisure a representative firm demands labor as the sole input to a stochastic production technology driven by general possibly nonmultiplicative shocks for cobb douglas utility and multiplicative shocks labor is nonstochastic and consumption and stock market volatility are equated as under no human capital deviations from this are analyzed for logarithmic utility and constant elasticity of substitution production technology cases are identified where the presence of labor causes consumption to be smoother than the stock market

factor intensities and factor substitution in general equilibrium abstract this article examines how factor intensity rankings between industries and the economy wide asymmetry in the degree of factor substitution combine to influence the manner in which changes in relative commodity prices affect the factoral distribution of income the reciprocal influence of factor endowment changes on the composition of outputs is also discussed the analysis is undertaken in a general three factor two commodity framework the minimal sized model that allows both influences to affect factor prices and admits of the possibility of complementarity between factors factors which are good substitutes find their returns behave somewhat similarly when commodity prices change while factors which are complements experience strongly asymmetrical fortunes a crucial role is played by a comparison of the share of the middle factor in each sector

nontraded asset valuation with portfolio constraints a binomial approach we provide a simple binomial framework to value american style derivatives subject to trading restrictions the optimal investment of liquid wealth is solved simultaneously with the early exercise decision of the nontraded derivative noshort sales constraints on the underlying asset manifest themselves in the form of an implicit dividend yield in the risk neutralized process for the underlying asset one consequence is that american call options may be optimally exercised prior to maturity even when the underlying asset pays no dividends applications to executive stock options eso are presented it is shown that the value of an eso could be substantially lower than that computed using the black scholes model we also analyze nontraded payoffs based on a price that is imperfectly correlated with the price of a traded asset the economics of asset pricing when one or more of the assets in the opportunity set are either subject to trading restrictions or entirely nontraded is a matter of great interest viewed from a practical perspective we have several important examples of such assets that are subject to trading restrictions pensions which represent perhaps the most significant of assets held by individual households are subject to trading restrictions it is typically the case that assets in pensions are not available for immediate consumption borrowing against pension assets is subject to significant direct and indirect costs by way of taxes and early withdrawal penalties human capital is another example housing investment is also illiquid and subject to significant transaction costs together pensions human capital and housing constitute a substantial part of a typical household s assets the significance of such nontraded assets for risk premia has already been noted by bewley 1982 there are other circumstances where lack of unrestricted trading plays an important role executive compensation plans usually take the this article was presented at boston university we would like to thank the editor bernard dumas and two anonymous referees for very helpful comments we also thank nalin kulatilaka and seminar participants for useful suggestions ganlin chang fei guan and carlton osakwe provided valuable research assistance j detemple acknowledges support from the social sciences and humanities research

lifetime investment and consumption using a defined contribution pension scheme during the accumulation phase of a defined contribution pension scheme a scheme member invests part of their stochastic income in a portfolio of a stock and a bond in order to build up sufficient funds for retirement it is assumed that the remainder of their salary pre retirement is consumed an annuity is purchased at retirement and the stock allocation and consumption pre retirement maximise the total expected lifetime consumption using a cara utility function perfect correlation between the scheme member s income and the stock price leads to analytical expressions for the controls for a general income model if the correlation is imperfect then analytical controls are found for two particular stochastic income models

the economic valuation of saltwater marsh supporting marine recreational fishing in the southeastern united states abstract this paper is concerned with placing an economic value on the contribution of wetlands in supporting recreational fishing in the southeastern united states a production function first links the recreational catch to angler fishing effort and wetlands the parameters of the recreational fisheries production function are estimated using cross sectional data by states to simplify the mathematics the estimated elasticities are substituted into a cobb douglas production function for simplicity a linear demand curve for recreational fishing is postulated which shifts when there is an increase or decrease in the catch success rate therefore incremental changes in wetlands will via the production function provide incremental changes in the catch which will in turn shift the recreational demand curve thereby increasing or decreasing consumer surplus using a discount rate of 8 125 the perpetual flow of consumer surplus per incremental acre of wetlands has an estimated asset value of 6 471 and 981 on the east and west coast of florida respectively in 1984 dollars if commercial fisheries and other economically useful functions of wetlands are added to recreational fisheries it may be more efficient for the state of florida to acquire more coastal land for preservation from development

optimal consumption and portfolio policies when asset prices follow a diffusion process abstract we consider a consumption portfolio problem in continuous time under uncertainty a martingale technique is employed to characterize optimal consumption portfolio policies when there exist nonnegativity constraints on consumption and on final wealth we also provide a way to compute and verify optimal policies our verification theorem for optimal policies involves a linear partial differential equation unlike the nonlinear partial differential equation of dynamic programming the relationship between our approach and dynamic programming is discussed we demonstrate our technique by explicitly computing optimal policies in a series of examples in particular we solve the optimal consumption portfolio problem for hyperbolic absolute risk aversion utility functions when the asset prices follow a geometric brownian motion the optimal policies in this case are no longer linear when nonnegativity constraints on consumption and on final wealth are included by these examples one can see that our approach is much easier than the dynamic programming approach

optimal consumption and investment under time varying liquidity constraints we study consumption and investment decisions given realistic time varying constraints on borrowing we first consider the case where borrowing is constrained by a maximum debt to income ratio we then consider collateral borrowing with a maximum loan to value ratio the resulting implications for optimal policies differ considerably from those obtained in the existing literature based on fixed borrowing limits but are consistent with those documented in the empirical literature

valuing environmental functions tropical wetlands recent studies have suggested that tropical wetland systems may have a crucial economic role to play in development the following paper provides an overview of these benefits using the general framework of cost benefit analysis as the methodological approach to assessing wetland values an analysis of trade offs between conserving or converting tropical wetlands demonstrates that taking into account the opportunity cost of wetland loss leads to a lower level of conversion than would otherwise be the case finally the paper discusses the extensions and limitations of the production function approach as applied to valuing nonmarketed wetland benefits

labor income and risky investments can part time farmers compete abstract in the developed countries a majority of farm households receive at least as much income from nonfarm sources as from the farm such part time farms have survived inspite of lower returns than full time farms this paper considers when lower returns to part time farming could be compensated by risk reduction due to diversification of income sources the paper uses a dynamic portfolio choice model with labor income the model and results could be applied in other contexts as well

optimal asset allocation with fixed term securities we investigate the optimal asset allocation of an investor who can invest in a fixed term security that is only traded at time 0 using a generalized martingale approach we solve the investor s optimal portfolio problem determine the optimal allocation to fixed term securities and provide a representation of trading strategies in terms of a liquidity related derivative we apply our approach to two benchmark scenarios fixed term fixed rate bank deposits and unspanned closed end securities that can only be traded at time 0 we show that both can be key parts of the investor s optimal asset mix and we investigate the dependence of optimal allocations to fixed term investments implied liquidity premia and other characteristics on the underlying model parameters

valuation optimal asset allocation and retirement incentives of pension plans we provide a framework in which we link the valuation and asset allocation policies of defined benefits plans with the lifetime marginal productivity schedule of the worker and the pension plan formula in turn we examine the retirement policies that are implied by the primitives of the model and the value of pension obligations our model provides an explicit valuation formula for a stylized defined benefits plan the optimal asset allocation policies consist of the replicating portfolio of the pension liabilities and the growth optimum portfolio independent of the pension liabilities we show that the worker will retire when the ratio of pension benefits to current wages reaches a critical value which depends on the parameters of the pension plan and the discount rate using numerical techniques we analyze the feedback effect of retirement policies on the valuation of plans and on the asset allocation decisions article published by oxford university press on behalf of the society for financial studies in its journal the review of financial studies

do open access conditions affect the valuation of an externality estimating the welfare effects of mangrove fishery linkages in thailand mangroves are considered ecologicallyimportant due to their role as breedinggrounds and nursery habitats for off shorefisheries however mangrove deforestationthrough conversion to shrimp aquaculturethreatens this valuable function this paperdevelops a dynamic production functionapproach to analyze the influence of habitatchanges on an open access fishery that faces afinite elasticity of demand the basic modelis applied to a case study of the impacts ofmangrove deforestation on the artisanal marinedemersal and shellfish fisheries in thailand by estimating parameters through pooledtime series and cross sectional data over the1983 1993 period for the five coastal zones ofsouthern thailand the welfare impacts ofmangrove deforestation are estimated underdifferent elasticity of demand assumptions under pure open access the welfare lossesestimated for mangrove deforestation inthailand of 30 km2 annually ranged from 12 000 to 408 000 depending on theelasticity of demand

capital income taxation and international portfolio choice abstract distortionary proportional capital income taxation is shown to cause both static effects via portfolio re allocation and dynamic effects via changes in the value of a claim to future transfers as well as via perceived changes in the future investment opportunity set the stochastic structure of returns to investment is important for understanding the consequences of a unilateral increase in the domestic tax rate a government choosing optimal tax policy makes a tradeoff between the increase in the perceived value of future transfers and the distortion to portfolio allocation produced by taxation with corporate taxation the optimal tax rate is positive

precautionary savings and the permanent income hypothesis this paper derives the explicit solution of a dynamic stochastic optimal consumption problem for infinitely lived agents whose preferences exhibit in the presence of non diversifiable labour income uncertainty a constant elasticity of intertemporal substitution and constant absolute risk aversion the constancy of the elasticity of intertemporal substitution which implies that marginal utility at zero consumption is infinite guarantees that the non negativity constraint on consumption is never binding along the optimal path the assumption of constant absolute risk aversion allows an explicit computation of human wealth and provides a simple representation of the precautionary savings motive

a note on the stability of the harris todaro model with capital mobility the present note derives the exact stability condition for the harris todaro model with intersectoral capital mobility where land is explicitly included as a third scarce factor in agriculture while the previous study by neary states the difficulty of deriving a clear cut result in such a case this note demonstrates that if capital and land are never technologically substitutes in the agriculture production neary s condition that the urban sector is more capital abundant than the rural sector becomes a sufficient condition for local stability in an important article in this journal neary 1981 considered the stability of the harris todaro model with intersectoral capital mobility among other things neary showed that when relative commodity prices are fixed and capital and labour are subject to constant returns to scale in agriculture an unspecialized equilibrium is dynamically stable if and only if the urban sector is capital abundant relative to the rural sector however in the original work by harris and todaro 1970 the fixed availability of land is included in the agriculture production function hence strictly speaking the stability condition quoted above is not for the original harris todaro model with intersectoral capital mobility on this point neary concluded that the introduction of a third scarcefactor land in agriculture greatly complicates the analysis and makes it impossible to derive simple and clear cut results the present note argues that a definite result can be derived if the normality property of factors of production which was utilized by rader 1968 and suzuki 1985 is assumed

robustly strategic consumption portfolio rules with informational frictions this paper provides a tractable continuous time constant absolute risk aversion gaussian framework to explore how the interactions of fundamental uncertainty model uncertainty due to a preference for robustness and state uncertainty due to information processing constraints rational inattention affect strategic consumption portfolio rules and precautionary savings in the presence of uninsurable labor income specifically after solving the model explicitly i compute and compare the elasticities of strategic asset allocation and precautionary savings to risk aversion robustness and inattention furthermore for plausibly estimated and calibrated model parameters i quantitatively analyze how the interactions of model uncertainty and state uncertainty affect the optimal share invested in the risky asset and show that they can provide a potential explanation for the observed stockholding behavior of households with different education and income levels this paper was accepted by neng wang finance

unemployment risks and optimal retirement in an incomplete market we develop a new approach for solving the optimal retirement problem for an individual with an unhedgeable income risk the income risk stems from a forced unemployment event which occurs as an exponentially distributed random shock the optimal retirement problem is to determine an individual s optimal consumption and investment behaviors and optimal retirement time simultaneously we introduce a new convex duality approach for reformulating the original retirement problem and provide an iterative numerical method to solve it reasonably calibrated parameters say that our model can give an explanation for lower consumption and risky investment behaviors of individuals and for relatively higher stock holdings of the poor we also analyze the sensitivity of an individual s optimal behavior in changing her wealth level investment opportunity and the magnitude of preference for postretirement leisure finally we find that our model explains a countercyclical pattern of the number of unemployed job leavers

an intertemporal general equilibrium asset pricing model the case of diffusion information this paper provides sufficient conditions for the equilibrium price system and a vector of exogenously specified state variable processes to form a diffusion process in a pure exchange economy the conditions involve smoothness of agents utility functions and certain nice properties of the aggregate endowment process and the dividend processes of traded assets in place of the dynamic programming a martingale representation technique is utilized to characterize equilibrium portfolio policies this technique is useful even when there does not exist a finite dimensional markov structure in the economy and thus the markovian stochastic dynamic programming is not applicable a gents are shown to hold certain hedging mutual funds and the riskless asset in contrast to earlier results the market portfolio does not have a special role in hedging since the markets are dynamically complete when there exists a finite dimensional markov system in the economy the dimension of the hedging demand identified through the markovian dynamic programming may be much larger than that identified by the martingale method copyright 1987 by the econometric society

hedging in incomplete markets with hara utility in the context of merton s original problem of optimal consumption and portfolio choice in continuous time this paper solves an extension in which the investor is endowed with a stochastic income that cannot be replicated by trading the available securities the problem is treated by demonstrating using analytic and in particular viscosity solutions techniques that the value function of the stochastic control problem is a smooth solution of the associated hamilton jacobi bellman hjb equation the optimal policy is shown to exist and given in a feedback form from the optimality conditions in the hjb equation at zero wealth a fixed fraction of income is consumed for large wealth the original merton policy is approached we also give a sufficient condition for wealth under the optimal policy to remain strictly positive

precautionary saving and portfolio allocation dp by gmm abstract there is much research on consumption savings problems with risky labor income and a constant interest rate and also on portfolio allocation with risky returns but non stochastic labor income less is known quantitatively about the interaction between the two forms of risk under crra utility undiversifiable income risk should be reflected in both savings rates and portfolio allocations to quantify these effects in a model of consumption and portfolio choice we adopt a semi parametric projection method for solving dynamic programmes based on generalized method of moments estimation of the parameters of approximate decision rules we find that background income risk does affect optimal portfolios but that this effect may be difficult to detect empirically

dynamic asset allocation in a mean variance framework the aim of this article is to analyze the portfolio strategies that are mean variance efficient when continuous rebalancing is allowed between the current date 0 and the horizon t under very general assumptions when a zero coupon bond of maturity t exists the dynamic efficient frontier is a straight line the slope of which is explicitly characterized every dynamic mean variance efficient strategy can be viewed as buy and hold combinations of two funds the zero coupon bond of maturity t and a continuously rebalanced portfolio an appropriate dynamic strategy defining the latter is explicitly derived for two particular price processes and comparisons of the efficient frontiers static versus dynamic are provided in these cases

theory and estimation of the household production function for wildlife recreation abstract the household production function is an intuitively appealing way to model man s interaction with nature this paper models the interaction between the household s behavior and publicly provided inputs into wildlife recreation the paper shows how to compute benefits assuming that the household production function is known the household production function approach collapses to the simple travel cost approach when households are unable to substitute their own inputs for publicly provided inputs in addition the paper demonstrates the conditions under which the parameters of cost and preference functions can be identified the conditions for identification are quite restrictive when several choices are endogenous

two trees with heterogeneous beliefs spillover effect of disagreement in a model where investors disagree about the fundamentals of two stocks the state price density depends on investor disagreements for both stocks especially the larger stock this implies that disagreement among investors in a large firm has a spillover effect on the pricing of other stocks owned by these investors the pricing effects of investor disagreements crucially depend on the average belief biases empirical findings support the novel model prediction of a disagreement spillover effect and help reconcile some mixed evidence in the literature

nontraded assets in incomplete markets pricing and portfolio choice this paper examines portfolio choice and asset pricing when some assets are nontraded for instance when a country cannot trade claims to its output on world capital markets when a government cann

valuing the environment as input review of applications to mangrove fishery linkages the following paper reviews recent developments in the methodology for valuing the role of wetlands in supporting economic activity the main focus will be on mangroves serving as a breeding ground and nursery habitat in support of coastal and marine fisheries as this particular ecological function of a mangrove system means that it is effectively an unpriced environmental input into fisheries then it is possible to value this contribution through applying the production function approach the first half of the paper overviews the procedure for valuing the environment as an input applied to the case of a wetland supporting a fishery both the static ellis fisher freeman approach and the dynamic approach developed by barbier and strand incorporating the intertemporal bioeconomic fishing problem are reviewed the second half of the paper discusses briefly two recent case studies of mangrove fishery valuation an application in south thailand which is based on the static ellis fisher freeman model and an application in campeche mexico which is based on the dynamic approach 2000 elsevier science b v all rights reserved

explicit solutions to an optimal portfolio choice problem with stochastic income abstract this paper solves in closed form the optimal portfolio choice problem for an investor with negative exponential utility over terminal wealth facing imperfectly hedgeable stochastic income the returns on income and the stock are imperfectly correlated so the market is incomplete we identify how an investor adjusts their merton rev econ statist 51 1969 247 portfolio of the stock and riskless asset via an intertemporal hedging demand in reaction to the stochastic income under general assumptions on the process governing the income the sign of the hedging demand is the opposite of the sign of the correlation between the income and stock the optimal portfolio in the stock is long stock if the risk premium is positive and correlation negative and short if these signs are reversed specializing in turn to normally distributed income and lognormally distributed income with or without mean reversion the effect of a number of parameters on the optimal portfolio in the stock can be studied when the risk premium on the stock and correlation have opposite signs the optimal portfolio decreases in magnitude with risk aversion unhedgeable variance of income and time and increases in magnitude with the magnitude of correlation under both the lognormal without mean reversion and normal models for income these relationships do not necessarily hold if the signs on the risk premium and correlation are the same in particular the optimal portfolio is not necessarily monotone in risk aversion violating well known static results in models without income when income follows a lognormal model with mean reversion more complicated behavior can occur for instance the optimal portfolio does not have to be monotonic in time regardless of the signs of correlation and the risk premium

optimal hedging in a dynamic futures market with a nonnegativity constraint on wealth abstract this paper examines the issue of optimal hedging demands for futures contracts from an investor who cannot freely trade his portfolio of primitive assets in the context of lognormal rather than normal returns and of a constant absolute risk aversion utility function in this context the nonnegativity constraint on wealth is binding and the optimal hedging demands are not identical with those encountered in the bulk of the literature which has largely overlooked this problem negative results concerning the derivation of equilibrium in the futures markets and the computation of the open interests then follow

the value of environment across efficiency quantiles a conditional regression quantiles analysis of rangelands beef production in north eastern australia in agricultural systems the value of environmental inputs can be measured using the production function approach whereby the marginal contributions of factors are associated with a shadow value under perfect competition and rationality assumptions however empirical studies show that inefficiency in production is common indicating that the rationality assumption is not met furthermore substantial evidence exists to suggest that the contributions of environmental inputs in particular may be differentiated across the efficiency distribution this means that the frontier technology may not be an appropriate reflection of the technology in use by inefficient enterprises this article presents the use of conditional regression quantiles to consider how the value of environmental inputs measured by their contributions to production vary across efficiency quantiles we employed a case study of rangelands beef production in australia to consider how environmental health differentially contributes to production values across efficiency quantiles our approach generates detailed insights into the nature of environmentally sourced technical inefficiency and suggests that conditional quantile regression approaches are ideal for consideration of issues wherein substantial heterogeneity exists limiting the information content of conditional mean based analyses

consumption and portfolio choice under internal multiplicative habit formation this paper explores the optimal consumption and investment behavior of an individual who derives utility from the ratio between his consumption and an endogenous habit we obtain closed form policies under general utility functionals and stochastic investment opportunities by developing a nontrivial linearization to the budget constraint this enables us to explicitly characterize how habit formation affects the marginal propensity to consume and optimal stock bond investments we also show that in a setting that combines habit formation with epstein zin utility consumption no longer grows at unrealistically high rates at high ages and investments in risky assets decrease

depletion of the environmental basis for renewable resources the economics of interdependent renewable and nonrenewable resources abstract this paper synthesizes familiar theories of nonrenewable and renewable resource economics in a two sector partial equilibrium analysis of efficient trade offs between renewable resource production and environmental development the irreversible impacts of coastal zone development provide a motivating example while development proceeds the efficient harvest of renewable resources may exceed the sustainable rate while development may involve several periods of growth and decline once development begins it proceeds without significant interruptions if a profitable renewable sector survives development ceases before exhausting all profitable opportunities interdependent stocks reduce distinctions between resource types because each sector exhibits features of the other

consumption and portfolio policies with incomplete markets and short sale constraints the infinite dimensional case abstract we employ a martingale approach to study a dynamic consumption portfolio problem in continuous time with incomplete markets and short sale constraints we introduce a notion of minimax local martingale and transform the dynamic problem into a static problem of maximizing expected utility over the consumption bundles that satisfy a single budget constraint formed using that measure we establish the existence of and characterize the minimax local measure provide sufficient conditions for the dynamic consumption portfolio problem to have a solution and relate the optimal policies to the solution of quasi linear partial differential equation

optimal risk taking with flexible income we study the portfolio selection problem of an investor who can optimally exert costly effort for more income the possibility of generating more income if necessary increases the risk taking appetite of the investor we find the optimal allocation to the risky security as a proportion of financial wealth and as a proportion of the total wealth defined as the combination of the financial wealth and the human capital of the investor when the investor s objective is the maximization of the terminal wealth we show that the optimal allocation to the risky security is a hump shaped function of the investment horizon however when the investor maximizes utility from intertemporal consumption the optimal allocation in the risky security is a constant proportion of the total wealth of the investor

optimal consumption investment policies with undiversifiable income risk and liquidity constraints abstract this paper examines the continuous time optimal consumption and portfolio choice of an investor having an initial wealth endowment and an uncertain stream of income from non traded assets the income stream is not spanned by traded assets and the investor is not allowed to borrow against future income so the financial market is incomplete we solve the corresponding stochastic control problem numerically with the markov chain approximation method prove convergence of the method and study the optimal policies in particular we find that the implicit value the agent attaches to an uncertain income stream typically is much smaller in this incomplete market than it is in the otherwise identical complete market our results suggest that this is mainly due to the presence of liquidity constraints

international investment barriers in general equilibrium abstract this paper examines quantitative international investment barriers in a general equilibrium model the constraints force otherwise similar agents to hold different portfolios of risky assets we show that this induces lending and borrowing this in turn instroduces a hedging motive against shifts in the interest rate the factors affecting agents portfolio choice the allocation of capital across countries as well as the interest rate are charcterized we conjure that the equilibrium world interest rate will be lower in the constrained situations than with free capital flows

the elephant in the ground managing oil and sovereign wealth many oil exporters accumulate large sovereign wealth funds though their portfolio allocation does not take into account below ground assets like oil similarly the above ground portfolio does not affect the decision to extract oil this paper shows that subsoil oil wealth should change a country s above ground asset allocation in two ways first the holding of all risky assets is leveraged because there is additional wealth outside the fund second more less is invested in financial assets that are negatively positively correlated with oil to hedge against the riskiness of subsoil exposure furthermore if marginal oil rents move pro cyclically with the value of the financial assets in the fund then oil will be extracted slower than predicted by the standard hotelling rule this leaves a buffer of oil to be extracted when both oil prices and asset returns are high finally any unhedged residual volatility must be managed through additional precautionary saving