repeated moral hazard and contracts with memory the case of risk neutrality we consider a repeated moral hazard problem where both the principal and the wealth constrained agent are risk neutral in each of two periods the agent can exert unobservable effort leading to success or failure incentives provided in the second period act as carrot and stick for the first period so that the effort level induced in the second period is higher after a first period success than after a failure if renegotiation cannot be prevented the principal may prefer a project with lower returns i e a project may be too good to be financed or similarly an agent can be overqualified this article offers a new perspective on dynamic moral hazard problems consider a riskneutral principal who can hire a risk neutral but wealth constrained agent the agent can exert unobservable effort which increases the likelihood of success in the one shot problem there is a well known trade off between effort incentives and rent extraction which leads to a downward distorted effort level compared to the first best solution we extend the standard model by assuming that there is a second period in which the principal can make an investment to continue the project and the agent can again exert unobservable effort it turns out that there are several interesting insights that so far have escaped the literature on repeated moral hazard which was focused on the case of risk averse agents in particular if the principal can commit not to renegotiate the second period incentives can be used to partially circumvent the limited liability constraint in the second period the principal induces the agent to choose a particularly high effort level following a first period success and a particularly low effort level following a first period failure the prospect of a higher second period rent following a first period success motivates the agent to exert more effort in the first period i e rents in the second period act as reward and punishment for the first period it should be emphasized that we assume no technological impact of a first period success or failure on the second period technology nevertheless an optimal dynamic contract exhibits memory hence if an outsider observed today a principal agent pair that was successful and another identical pair that was not successful he would be right to predict that the first pair also is more likely to succeed tomorrow in other words a serial correlation across periods which we sometimes refer to as a hot hand effect is generated endogenously merely based on incentive considerations 2

rational panics and stock market crashes abstract this paper offers an explanation for stock market crashes which focuses on the role of rational but uninformed traders we show that uninformed traders can precipitate a price crash because as prices decline they surmise that informed traders received negative information which leads them to reduce their demand for assets and drive the price of stocks even lower the model yields several implications such as that crashes can occur even when the fundamentals are strong and that the magnitude of the crash depends on the fraction of uninformed investors and the amount of unsophisticated passive investing present in the market

financial contracting theory meets the real world an empirical analysis of venture capital contracts we compare the characteristics of real world financial contracts to their counterparts in financial contracting theory we do so by studying the actual contracts between venture capitalists vcs and entrepreneurs the distinguishing characteristic of vc financings is that they allow vcs to separately allocate cash flow rights board rights voting rights liquidation rights and other control rights we describe and measure these rights we then interpret our results in relation to existing financial contracting theories we also describe the interrelation and the evolution across financing rounds of the different rights query 1 query 2

stochastic equilibria existence spanning number and the no expected financial gain from trade hypothesis stochastic equilibria under uncertainty with continuous time security trading and consumption are demonstrated in a general setting a common question is whether the current price of a security is an unbiased predictor of the future price of the security plus intermediate dividends this is the hypothesis of no expected financial gains from trade the relevance of this hypothesis in multi good economies is called into question by the following demonstrated fact for each set of probability assessments there exists a corresponding equilibrium one with the original agents original equilibrium allocations and no expected financial gains from trade under the given probability assessments the spanning number of the economy is defined as the fewest number of security markets required to sustain a complete markets equilibrium in a dynamic sense made precise in the paper the spanning number is linked directly to agent primitives in particular the manner in which new information resolves uncertainty over time the spanning number is shown to be invariant under bounded changes in expectations several examples are given in which the spanning number is finite even though the number of potential states of the world is infinite

knowledge accumulation within an organization in this article we consider a knowledge accumulation problem within an organization that cannot prevent the worker from quitting and using the knowledge outside the organization we show that knowledge accumulation is delayed the fraction of working time allocated to knowledge creation is highest at the early career stage falls gradually then rises again before falling finally toward zero we determine the effect of a change in the severity of the enforcement problem or the specificity of knowledge we also discuss the form of the optimal life cycle wage profiles the role of the initial knowledge level and the role of discounting

limited liability and incentive contracting with ex ante action choices abstract this article examines a principal agent model of financial contracting in which a risk neutral entrepreneur agent makes an unobservable ex ante effort choice while employing the investment funds of a risk neutral investor principal the key innovation is that the investment contract is subject to statutory liability limits given these liability limits two settings are considered one in which the investor payoff function is also constrained to be monotonically nondecreasing in firm profit and another in which no such monotonic contract constraint is imposed in the former case a standard debt contract is shown to emerge and a first best effort choice is not achieved in the latter setting the optimum is characterized by a live or die payoff function and a first best effort level may or may not be realized

unforeseen contingencies and incomplete contracts we scrutinize the conceptual framework commonly used in the incomplete contract literature this literature usually assumes that contractual incompleteness is due to the transaction costs of describing or of even foreseeing the possible states of nature in advance we argue however that such transaction costs need not interfere with optimal contracting i e transaction costs need not be relevant provided that agents can probabilistically forecast their possible future payoffs even if other aspects of the state of the nature cannot be forecast in other words all that is required for optimality is that agents be able to perform dynamic programming an assumption always invoked by the incomplete contract literature the foregoing optimality result holds very generally provided that parties can commit themselves not to renegotiate moreover we point out that renegotiation may be hard to reconcile with a framework that otherwise presumes perfect rationality however even if renegotiation is allowed the result still remains valid provided that parties are risk averse

renegotiation design with unverifiable information this paper considers a buyer seller relationship with observable but unverifiable investments and or random utility parameters in such situations it is known that contract renegotiation may prevent the implementation of first best outcomes in this paper we show however that efficient investments and optimal risk sharing can typically be achieved provided the initial contract is able to monitor the ex post renegotiation process specifically we focus on the following two features of renegotiation design first default options in case renegotiation breaks down second the allocation of all bargaining power to either contracting party moreover we show that these two features can be obtained in standard rubinstein bargaining games through contractual provisions such as specific performance clauses and penalties for delay or equivalently financial hostages refundable without interest

exit option in hierarchical agency abstract we explain why organizations that limit the voice of their agents can benefit from granting them an exit option we study a hierarchy with a principal a productive supervisor and an agent communication is imperfect in that only the supervisor can communicate with the principal while the agent has no direct voice to the principal we show that the principal is better off if she grants the agent the option to walk away from the contract by doing so the principal is implicitly giving a veto power to the agent this in turn restricts the manipulation of report by the supervisor thus the exit option can be interpreted as a remedy for limits on communication our finding contrasts to the traditional result from the contract theory literature that the exit option reduces the principal s welfare while protecting the agent our result is robust to the case of collusion between the supervisor and the agent we also examine the optimal exit option i e whether exit should entail a payment to or from the agent

dynamic equilibrium with liquidity constraints this article studies an intertemporal economy with liquidity constrained and unconstrained individuals we use a stopping time approach to solve the finite horizonconstrained consumption portfolio problem with constant relative risk aversion and to examine the structure of equilibrium the impact of the constraint on the optimal consumption and the financing portfolio is assessed the equilibrium state price density is related to the exercise boundary of an american style contingent claim with nonlinear payoff this stopping time characterization enables us to prove the existence of an equilibrium and can be implemented numerically properties of equilibrium bond and stock returns are examined copyright 2003 oxford university press

the role of portfolio constraints in the international propagation of shocks we study the comovement among stock prices and exchange rates in a three good three country centre periphery dynamic equilibrium model in which the centre s agents face portfolio constraints we characterize equilibrium in closed form for a broad class of portfolio constraints solving for stock prices terms of trade and portfolio holdings we show that portfolio constraints generate wealth transfers between the periphery countries and the centre which increase the comovement of the stock prices across the periphery we associate this excess comovement caused by portfolio constraints with the phenomenon known as contagion the model generates predictions consistent with other important empirical results such as amplification and flight to quality effects copyright 2008 wiley blackwell

an enhanced robustness approach for managing supply and demand uncertainties abstract managing supply and demand uncertainties is a topic that receives increasing management attention due to 1 more price based competitions forcing firms purchase from cheaper but less reliable or unproven suppliers and 2 undesirable consequences of unaddressed demand fluctuations such as reduced service level financial loss reputational damage and loss of market share this paper presents a realistic production distribution planning model that is robust to common supply interruptions and demand variations a robustness approach named elastic p robustness is introduced that obviates the need to estimate probability distribution of random parameters when managing operational uncertainties of the supply chain the application of the proposed approach is investigated in an actual organization from discrete durable parts manufacturing sector our analyses of numerical results focus on 1 exploring different tactics for managing supply and demand variations 2 examining the benefits of concurrent consideration of supply and demand uncertainties 3 benchmarking the performance of the proposed approach against the popular robustness algorithms and 4 investigating the price of robustness under various supply and demand scenarios

security design with status concerns abstract this paper provides a status based explanation for convertible securities an entrepreneur with status concerns inducing risk taking decides how to finance the firm and how to dynamically manage it solving analytically for the optimal security we find that it is substantially similar to a convertible security our model can explain why convertible securities are mainly issued by start ups and small firms as we show that their salient characteristics higher volatility and dynamic flexibility accentuate incentives to issue convertible securities we also provide analytical results relevant to quantifying how status concerns affect credit risk an established factor behind security choice

cooperative investments and the value of contracting recent articles have shown that contracts can support the efficient outcome for bilateral trade even in the face of specific investments and incomplete contracting these studies typically considered selfish investments that benefit the investor e g the seller s investment reduces her production costs the authors find very different results for cooperative investments that directly benefit the investor s partner e g the seller s investment improves the buyer s value of the good most importantly if committing not to renegotiate the contract is impossible then contracting has no value i e the parties cannot do better than to abandon contracting altogether in favor of ex post negotiation

an asset pricing view of external adjustment abstract recent literature has argued that conventional measures of external sustainability the trade balance and current account are misleading because they omit capital gains on net foreign asset positions we adjust the definition of the current account to include the capital gains and discuss how this may affect our thinking about external adjustment and sustainability we do so in the context of a two country macro finance model of pavlova and rigobon 2008a that allows exploration of the interconnections between equilibrium portfolios and external accounts dynamics we calibrate the model and find that it generates several testable implications some of which have already been validated empirically first we establish dynamic properties of the capital gains adjusted current account and show that they are fundamentally different from those of the conventional current account second we find that capital gains have a stabilizing effect on the trade balance and the current account finally we demonstrate that in response to a shock the conventional and the capital gains adjusted current accounts may move in opposite directions

renegotiation and optimality in agency contracts we analyse renegotiation in a hidden action principal agent model contract renegotiation offers are made by the agent a refinement is imposed on the principal s beliefs if precisely one action is optimal with respect to both the principal s and the agent s contracts the principal believes that that action has been taken with the refinement imposed perfect bayesian equilibrium allocations are identical to the second best in the classical principal agent model without renegotiation when renegotiation is led by the agent and when equilibria satisfy the refinement equilibrium allocations are ex ante efficient incentive contracting is a common mechanism for promoting ex ante investments and for avoiding ex post opportunistic behaviour in a long term or continuing economic relationship the classical principal agent model holmstrom 1979 grossman and hart 1983 is a natural framework for this class of problem in such a model a risk averse agent performs an action on behalf of a risk neutral principal the agent s action is unobservable and affects the principal s revenue in a random fashion the derivation and characterization of efficient compensation schemes have been the major focus in the principal agent literature generally the incentives to motivate a costly action from the agent take the form of profit sharing the agent s reward is made contingent on his random performance outcomes

ambivalent investment and the hold up problem in this paper we add to the foundations of incomplete contracting literature we study the hold up problem with ambivalent investment where investment benefits the investing party if ex post the right decision is undertaken but harms the investing party if the wrong decision is made in this context we show that the power of contracts to provide investment incentives depends on three factors the commitment value of contracts the amount of quasirents that the investing party can expect in the case of out of contract renegotiation and the degree of ambivalence of investment first contracts provide first best investment incentives when parties can commit to a contract regardless of the type of investment second with sufficiently ambivalent investment if parties cannot commit not to renegotiate a contract and if the investing party s bargaining power is intermediate contracts cannot improve investment incentives above those provided by no contract in contrast a simple buyer or seller option contract is optimal when the investing party s bargaining power is extreme jel d23 k12 l22

optimal consumption portfolio choices and retirement planning abstract we examine consumption and investment decisions in a life cycle model with habit formation stochastic opportunity set stochastic wages and labor supply flexibility retirement is taken into account by specifying an age at which labor earnings stop but consumption spending continues explicit solutions are obtained for optimal consumption labor supply and the financing portfolio we examine the structure and determinants of the optimal portfolio we also study the effects of the retirement date and of habits on optimal decisions finally we conduct a preliminary analysis to assess the effects of a liquidity constraint on optimal consumption leisure choices

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

stage financing and the role of convertible securities venture capital financing is characterized by extensive use of convertible securities and stage financing in a model where a venture capitalist provides staged financing for a project we illustrate an advantage of convertible debt or warrants over a mixture of debt and equity essentially when the venture capitalist retains the option to abandon the project the entrepreneur has an incentive to engage in window dressing and bias positively the short term performance of the project reducing the probability that it will be liquidated an appropriately designed convertible security prevents such behaviour because window dressing also increases the probability that the venture capitalist will exercise the conversion option becoming the owner of a substantial fraction of the project s equity

adverse selection in dynamic moral hazard this paper studies a multiperiod moral hazard problem under two assumptions i contracts are subject to renegotiations ii the agent s action has long term effects the action is also interpreted as a choice of characteristic or type renegotiation proof contracts that implement various actions including random ones are characterized under appropriate conditions the equilibrium involves the principal implementing a random action therefore the equilibrium has standard properties of adverse selection models

multiplicity in general financial equilibrium with portfolio constraints abstract this paper explores the role of portfolio constraints in generating multiplicity of equilibrium we present a simple financial market economy with two goods and two households households who face constraints on their ability to take unbounded positions in risky stocks absent such constraints equilibrium allocation is unique and is pareto efficient with one portfolio constraint in place the efficient equilibrium is still possible however additional inefficient equilibria in which the constraint is binding may emerge we show further that with portfolio constraints cum incomplete markets there may be a continuum of equilibria adding incomplete markets may lead to real indeterminacy

moral hazard hold up and the optimal allocation of control rights i examine the optimal allocation of control rights in a model with manager moral hazard where the manager and investor may hold up each other ex post the control allocation determines both the likelihood of hold up and the agents renegotiation payoffs in equilibrium only two control allocations are optimal either exclusive investor control or a contingent control allocation that allows the manager to remain in control if and only if interim performance is good thus my model explains why it may be optimal to link control to thefirm s performance such that managers retain control only following good performance

the consumption based capital asset pricing model the paper provides conditions on the primitives of a continuous time economy under which there exist equilibria obeying the consumption based capital asset pricing model ccapm the paper also extends the equilibrium characterization of interest rates of cox ingersoll and ross 1985 to multi agent economies we do not use a markovian state assumption this work provides sufficient conditions on agents primitives for the validity of the consumption based capital asset pricing model ccapm of breeden 1979 as a necessary condition breeden showed that in a continuous time equilibrium satisfying certain regularity conditions one can characterize returns on securities as follows the expected instantaneous rate of return on any security in excess of the riskless interest rate the security s expected excess rate of return is a multiple common to all securities of the instantaneous covariance of this excess return with aggregate consumption increments this common multiple is the arrow pratt measure of risk aversion of a representative agent rubinstein 1976 published a discrete time precursor of this result the exis tence of equilibria satisfying breeden s regularity conditions had been an open issue we also show that the validity of the ccapm does not depend on breeden s assumption of markov state information and present a general asset pricing model extending the results of cox ingersoll and ross 1985 as well as the discrete time results of rubinstein 1976 and lucas 1978 to a multi agent environment since the ccapm was first proposed much effort has been directed at finding sufficient conditions on the model primitives the given assets the agents preferences the agents consumption endowments and in a production econ omy the feasible production sets conditions sufficient for the existence of continuous time equilibria were shown in duffie 1986 but the equilibria demonstrated were not shown to satisfy the additional regularity required for the ccapm in particular breeden assumed that all agents choose pointwise interior consumption rates in order to characterize asset prices via the first order conditions of the bellman equation interiority was also assumed by huang 1987 in demonstrating a representative agent characterization of equilibrium an approach exploited here the use of dynamic programming and the bellman equation aside from the difficulty it imposes in verifying the existence of interior 1 financial support from the national science foundation is gratefully acknowledged we thank

rational asset pricing bubbles and portfolio constraints this article shows that portfolio constraints can give rise to rational asset pricing bubbles in equilibrium even if there are unconstrained agents in the economy who can benefit from the induced limited arbitrage opportunities furthermore it is shown that bubbles can lead to both multiplicity and real indeterminacy of equilibria the general results are illustrated by two explicitly solved examples where seemingly innocuous portfolio constraints make bubbles a necessary condition for the existence of an equilibrium c 2012 elsevier inc all rights reserved

justifying the first order approach to principal agent problems it is of interest to know when the incentive compatibility conditio n in principal agent problems can be replaced by the condition that the agent s expected utility be stationary in effort the mirrlees rogerson conditions do not work if the principal can observe more than one observable statistic also the mirrlees rogerson assumption that the distribution function of output is convex in the agent s action is unsatisfactory even in the context of the basi c model it is too restrictive the paper presents a suite of conditio ns that are applicable to the multistatistic case and replaces the objectionable convex distribution function assumption copyright 1988 by the econometric society

characterization of a risk sharing contract with one sided commitment in this paper i provide a stopping time based solution to a long term contracting problem between a risk neutral principal and a risk averse agent the agent faces a stochastic income stream and cannot commit to the long term contracting relationship to compute the optimal contract i also design an algorithm that is more efficient than value function iteration

tactical supply chain planning under a carbon tax policy scheme a case study greenhouse gas emissions are receiving greater scrutiny in many countries due to international forces to reduce anthropogenic global climate change industry and their supply chains represent a major source of these emissions this paper presents a tactical supply chain planning model that integrates economic and carbon emission objectives under a carbon tax policy scheme a modified cross entropy solution method is adopted to solve the proposed nonlinear supply chain planning model numerical experiments are completed utilizing data from an actual organization in australia where a carbon tax is in operation the analyses of the numerical results provide important organizational and policy insights on 1 the financial and emissions reduction impacts of a carbon tax at the tactical planning level 2 the use of cost emission tradeoff analysis for making informed decisions on investments 3 the way to price carbon for maximum environmental returns per dollar increase in supply chain cost

complexity and renegotiation a foundation for incomplete contracts the paper considers a hold up model where only one of n future trading opportunities will prove to be efficient and where ex post renegotiation of the ex ante contract cannot be prevented as the environment becomes more complex n the outcome under any message contingent long term contract converges to that of the incomplete contracting model where trade is contractible ex post but not ex ante when trades are costly to describe both ex ante and ex post the incomplete contracting result is extended to a broader class of environments

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

venture capital financing moral hazard and learning we consider the provision of venture capital in a dynamic agency model the value of the venture project is initially uncertain and more information arrives by developing the project the allocation of the funds and the learning process are subject to moral hazard the optimal contract is a time varying share contract which provides intertemporal risk sharing between venture capitalist and entrepreneur the share of the entrepreneur reflects the value of a real option the option itself is based on the control of the funds the dynamic agency costs may be high and lead to an inefficient early stopping of the project a positive liquidation value explains the adoption of strip financing or convertible securities finally relationship financing including monitoring and the occasional replacement of the management improves the efficiency of the financial contracting

a theory of debt and equity diversity of securities and manager shareholder congruence this paper shows how the optimal financial structure of a firm complements incentive schemes to discipline managers and how the securities return streams determine the claim holders incentives to intervene in management the theory rationalizes 1 the multipucity of securities 2 the observed correlation between return streams and control rights of securities and 3 the partial congruence between managerial and equity holder preferences over policy choices and monetary rewards as well as the low level of interference of equity in management the theory also offers new prospects for a reappraisal of the earlier corporate finance literature

courts contracts and interference this paper shows that the possibility of interference in court proceedings or more generally jamming other agents messages has significant consequences for the form of optimal contracts and the flexibility of decisions that can be made inside firms our approach offers a new view of authority basing it on the ability of parties to have their say in court interference gives authority a role in worlds where it is traditionally absent in contract theory like simple employment relationships without specific investments c 2002 published by elsevier science b v

financing and advising optimal financial contracts with venture capitalists this paper analyses the joint provision of effort by an entrepreneur and by an advisor to improve the productivity of an investment project without moral hazard it is optimal that both exert effort with moral hazard if the entrepreneur s effort is more efficient less costly than the advisor s effort the latter is not hired if she does not provide funds outside financing arises endogenously this explains why investors like venture capitalists are value enhancing the level of outside financing determines whether common stocks or convertible bonds should be issued in response to incentives

minimum payments and induced effort in moral hazard problems abstract consider a moral hazard problem in which there is a constraint to pay the agent no less than some amount m this paper studies the effect of changes in m on the effort that the principal chooses to induce from the agent we present sufficient conditions on the informativeness of the signal observed by the principal and on the agent s utility under which when m increases induced effort and hence productivity falls we also study how the cost minimizing contract for any given effort level varies in m we present an efficient algorithm for numerically calculating optimal contracts for given parameters and show that induced effort falls when m is increased in many cases even when our sufficient conditions fail

collateral constraints and asset prices abstract we study the effects of collateral constraints in an economy populated by investors with nonpledgeable labor incomes and heterogeneous preferences and beliefs we show that these constraints inflate stock prices and generate spikes and crashes in price dividend ratios and volatilities clustering of volatilities and leverage cycles they also lead to substantial decreases in interest rates and increases in sharpe ratios when investors are anxious about hitting constraints due to production crises in the economy furthermore stock prices have large collateral premiums over nonpledgeable incomes we derive asset prices and stationary distributions of the investors consumption shares in closed form

market liquidity hedging and crashes in the absence of significant news hedging strategies were blamed for the stock market crash of october 1987 but traditional models cannot explain how a relatively small amount of selling could cause so large a price drop the authors develop a rational expectations model in which prices play an important role in shaping expectations markets are much less liquid in their model than in traditional models discontinuities or crashes can occur even with relatively little hedging the model is consistent with theories as disparate as keynes beauty contest insights and thom s catastrophe analysis and suggests means to reduce volatility copyright 1990 by american economic association

heterogeneous preferences and equilibrium trading volume abstract the representative agent lucas model stresses aggregate risk and hence does not allow us to study the impact of agents heterogeneity on the dynamics of equilibrium trading volume in this paper we investigate under what conditions non informational heterogeneity i e differences in preferences and endowments leads to nontrivial trading volume in equilibrium we present a non informational no trade theorem that provides necessary and sufficient conditions for zero equilibrium trading volume in a continuous time lucas market model with heterogeneous agents multiple goods and multiple securities we explain in detail how no trade equilibria are related to autarky equilibria portfolio autarky equilibria and peculiar financial market equilibria which play an important role in the literature on international risk sharing

differences of opinion endogenous liquidity and asset prices this paper studies how investors differences of opinion affect liquidity and asset prices in our economy excessively optimistic investors are subject to an endogenous funding constraint that prevents default due to ex ante limited commitment when the funding constraint binds optimists use their savings to increase their consumption share deterring default this allows them to place speculative trades increasing market liquidity their losses on these trades make them prone to default leading to a renewed binding of the funding constraint this feedback between funding illiquidity disagreement and market liquidity is consistent with several empirical features of liquidity and financial asset prices

equilibrium asset prices with undiversifiable labor income risk abstract in a two period lucas tree economy in which ex ante identical but ex post dissimilar agents face undiversifiable labor income risk calibrating a wrong representative agent model results in overstating the equilibrium riskfree rate and in understating the equilibrium equity premium if the utility function exhibits decreasing absolute risk aversion and decreasing absolute prudence these behavioral assumptions provide as a consequence a theoretical rationale for the often advanced conjecture that nontraded risk contributes to the solution of the riskfree rate and equity premium puzzles

diversification as a public good community effects in portfolio choice within a rational general equilibrium model in which agents care only about personal consumption we consider a setting in which due to borrowing constraints individuals endowed with local resources underparticipate in financial markets as a result investors compete for local resources through their portfolio choices even with complete financial markets and no aggregate risk agents may herd into risky portfolios this yields a pareto dominated outcome as agents introduce community risk unrelated to fundamentals moreover if some agents are behaviorally biased or cannot completely diversify their holdings rational agents may choose more extreme portfolios and amplify the effect

moral hazard and capital structure dynamics we base a contracting theory for a start up firm on an agency model with observable but nonverifiable effort and renegotiable contracts two essential restrictions on simple contracts are imposed the entrepreneur must be given limited liability and the investor s earnings must not decrease in the realized profi to f thefirm all message game contracts with pure strategy equilibria and no third parties are considered within this class of contracts equilibria and regardless of who has the renegotiating bargaining power debt and convertible debt maximize the entrepreneur s incentives to exert effort these contracts are optimal if the entrepreneur has the bargaining power in renegotiation if the investor has the bargaining power the same is true unless debt induces excessive effort in the latter case a non debt simple contract achieves efficiency the non contractibility of effort does not lower welfare thus when the non contractibility of effort matters our results mirror typical capital structure dynamics an early use of debt claims followed by a switch to equity like claims

the mirrlees approach to mechanism design with renegotiation with applications to hold up and risk sharing the paper studies the implementation problem first analyzed by maskin and moore 1999 in which two agents observe an unverifiable state of nature and may renegotiate inefficient outcomes following play of the mechanism we develop a first order approach to characterizing the set of implementable utility mappings in this problem paralleling mirrlees s 1971 first order analysis of standard mechanism design problems we use this characterization to study optimal contracting in hold up and risk sharing models in particular we examine when the contracting parties can optimally restrict attention to simple contracts such as noncontingent contracts and option contracts where only one agent sends a message

financial entanglement a theory of incomplete integration leverage crashes and contagion abstract we propose a unified model of limited market integration asset price determination leveraging and contagion investors and firms are located on a circle and access to markets involves participation costs that increase with distance due to a complementarity between participation and leverage decisions the equilibrium may exhibit diverse leverage and participation choices across investors although investors are ex ante identical small changes in market access costs can cause a change in the type of equilibrium leading to discontinuous price changes deleveraging and portfolio flow reversals moreover the market is subject to contagion an adverse shock to investors in some locations affects prices everywhere jel d83 g11 g12 g32 g35

an explicit bound on individual assets deviations from apt pricing in a finite economy abstract ross s arbitrage pricing theory apt is a tractible and reasonable alternative to the mean variance model nonetheless understanding of the theory has been obscured by the complexity of the sequence economy models used for motivation by contrast we give a simple and direct derivation of the apt in a finite economy using an explicit bound on the deviations from apt prices across assets a coarse calculation shows that theoretical deviations from apt pricing are negligible in our economy

renegotiation of sales contracts this paper studies moral hazard contracts that may be renegotiated after an agent chooses an unobservable effort unlike in previous models a contract here contains only one compensation scheme and the agent has all the bargaining power in the renegotiation stage using a relatively weak forward induction refinement all equilibria are shown tb be second best efficient renegotiation occurs in every equilibrium if the effort set is rich the only equilibrium initial contract is a sales contract i e a scheme which sells the project to the agent this captures the idea that a party the principal who has an inherently weak renegotiation position will sometimes insist on a simple initial contract

the theory of moral hazard and unobservable behaviour part i principal agent models are studied in which outcomes conditional on the agent s action are uncertain and the agent s behaviour therefore unobservable for a model with bounded agent s utility conditions are given under which the first best equilibrium can be approximated arbitrarily closely by contracts relating payment to observable outcomes for general models it is shown that the solution may not always be obtained by using the agent s first order conditions as constraint general conditions of lagrangean type are given for problems in which contracts are finite dimensional 1 the moral hazard situation

endogenous completeness of diffusion driven equilibrium markets we study the existence of dynamic equilibria with endogenously complete markets in continuous time heterogenous agents economies driven by diffusion processes our main results show that under appropriate conditions on the transition density of the state variables market completeness can be deduced from the primitives of the economy in particular we prove that a sufficient condition for market completeness is that the volatility of dividends be invertible and provide higher order conditions that apply when this condition fails as is the case in the presence of fixed income securities in contrast to previous research our formulation does not require that securities pay terminal dividends and thus allows for both finite and infinite horizon economies

investment incentives debt and warrants abstract this paper models and characterizes investment incentive problems associated with debt financing the decision problem of residual claimants is explicity formulated and their investment policies are characterized the paper also analyzes the use of conversion features and warrants to control distortionary incentives these claims reverse the convex shape of levered equity over the upper range of the firm s earnings and this mitigates the incentive to take risk it is shown that under certain conditions such claims can be constructed to restore net present value maximizing incentives and simultaneously meet the financing requirements of the firm

monotone comparative statics under uncertainty this paper analyzes monotone comparative statics predictions in several classes of stochastic optimization problems the main results characterize necessary and sufficient conditions for comparative statics predictions to hold based on properties of primitive functions that is utility functions and probability distributions the results apply when the primitives satisfy one of the following two properties i a single crossing property which arises in applications such as portfolio investment problems and auctions or ii log supermodularity which arises in the analysis of demand functions affiliated random variables stochastic orders and orders over risk aversion

supply chain design for efficient and effective blood supply in disasters abstract the emergency supply of blood in natural and anthropogenic disasters has proved challenging this article presents a stochastic bi objective supply chain design model for the efficient cost minimizing and effective delivery time minimizing supply of blood in disasters the blood supply network under investigation is comprised of blood donors mobile blood facilities local and regional blood centers and demand points a hybrid solution approach combining the e constraint and lagrangian relaxation methods is developed to solve the proposed model our numerical experiments and subsequent discussions focus on 1 investigating the utility of the proposed model in solving different size problems 2 exploring possible tradeoffs between supply chain cost and delivery time 3 identifying the areas along the supply chain where investments can be made to improve supply chain efficiency and effectiveness and 4 performance benchmarking of the proposed stochastic programming approach

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

moral hazard with bounded payments we study the moral hazard problem with general constraints on how little or much the agent can be paid as a function of output we provide a characterization and existence result using only very simple methods in the dual problem of minimizing costs for a given effort level a constraint that harms the principal will always result in a contract that pays according to the constraint on some range of outcomes for the case of a simple fixed minimum feasible payment the resultant contract will be option like we show how the strike price and intensity of incentives once the strike price is exceeded vary in the minimum payment and the outside option of the agent when the principal can also choose the effort to induce then even if the constraint harms the principal he may optimally choose a contract that never pays the minimum or maximum we show that this can only occur if the problem without the payment constraints fails a form of concavity

debt constrained asset markets we develop a theory of general equilibrium with endogenous debt limits in the form of individual rationality constraints similar to those in the dynamic consistency literature if an agent defaults on a contract he can be excluded from future contingent claims markets trading and can have his assets seized he cannot be excluded from spot markets trading however and he has some private endowments that cannot be seized all information is publicly held and common knowledge and there is a complete set of contingent claims markets since there is complete information an agent cannot enter into a contract in which he would have an incentive to default in some state in general there is only partial insurance variations in consumption may be imperfectly correlated across agents interest rates may be lower than they would be without constraints and equilibria may be pareto ranked

an analysis of the principal agent problem most analyses of the principal agent problem assume that the principal chooses an incentive scheme to maximize expected utility subject to the agent s utility being at a stationary point an important paper of mirrlees has shown that this approach is generally invalid we present an alternative procedure if the agent s preferences over income lotteries are independent of action we show that the optimal way of implementing an action by the agent can be found by solving a convex programming problem we use this to characterize the optimal incentive scheme and to analyze the determinants of the seriousness of an incentive problem

renegotiating moral hazard contracts under limited liability and monotonicity in a principal agent model with unobservable effort and possible renegotiation contracts are assumed to satisfy two natural restrictions limited liability for the agent and monotonicity of payments for the principal the main result is that if the agent has the renegotiation bargaining power any contract is weakly pareto dominated by a debt contract journal of economic literature classification numbers d820 l140 o261

default and renegotiation a dynamic model of debt we analyze the role of debt in persuading an entrepreneur to pay out cash e ows rather than to divertthem in the e rstpartof the paper we study the optimal debt contract specie cally the trade off between the size of the loan and the repayment under the assumption that some debt contract is optimal in the second part we consider a more general class of nondebt contracts and derive sufficient conditions for debt to be optimal among these

nash equilibrium and welfare optimality if is a set of social alternatives a social choice rule scr assigns a subset of a to each potential profile of individuals preferences over a where the subset is interpreted as the set of welfare optima a game form or mechanism implements the social choice rule if for any potential profile of preferences 1 any welfare optimum can arise as a nash equilibrium of the game form implying in particular that a nash equilibrium exists and 2 all nash equilibria are welfare optimal the main result of this paper establishes that any scr that satisfies two properties monotonicity and no veto power can be implemented by a game form if there are three or more individuals the proof is constructive

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

on trees and logs abstract in this paper we contrast the main workhorse model in asset pricing theory the lucas 1978 tree model lt model to a benchmark model in financial equilibrium theory the real assets model ra model it is commonly believed that the two models entail similar conclusions since the lt model is a special case of the ra model but this is simply wrong implications of these models can be strikingly at odds indeed under the widely used log linear specification of households preferences we show that for a large set of initial endowments the lt model even with potentially complete financial markets admits only peculiar financial equilibria in which the stock market is completely degenerate in that all stocks offer the same investment opportunity and yet allocation is pareto optimal we investigate why the lt model is so much at variance with the ra model and uncover new results on uniqueness of financial equilibria and introduction of portfolio constraints obtaining in the lt model but not in the ra model