temptation and social security in a dynastic framework abstract we investigate welfare and aggregate implications of a pay as you go payg social security system in a dynastic framework in which individuals have self control problems the presence of self control problems induces individuals to save less because of their urge for temptation towards current consumption individuals efforts to balance between the short term urge for temptation and the long term commitment for consumption smoothing result in self control costs in this environment payg social security works as a self control cost reducing device in contrast the presence of altruism induces individuals to save more this in turn mitigates the adverse effects of self control problems and payg social security on savings but magnifies the self control costs we find that in our environment the adverse welfare effects of a payg system are further mitigated relative to the environments that incorporate altruism and self control issues separately however the level of mitigation is quite modest

50th anniversary article option pricing valuation models and applications this paper surveys the literature on option pricing from its origins to the present an extensive review of valuation methods for european and american style claims is provided applications to complex securities and numerical methods are surveyed emphasis is placed on recent trends and developments in methodology and modeling

factorization of european and american option prices under complete and incomplete markets abstract in a standard option pricing model with continuous trading and diffusion processes this paper shows that the price of one european style option can be factorized into two intuitive components one robust x 0 which is priced by arbitrage and a second 0 which depends on a risk orthogonal to the traded securities this result implies the following 1 in an incomplete market these parts represent the price of a hedging portfolio which is unique and a premium which depends only on the risk premiums associated with the residual risk respectively 2 in a complete market it allows factoring the contribution of the different sources of risk to the final option price for example in a stochastic volatility model we can quantify the impact on the option price of volatility risk relative to market risk 0 and x 0 respectively hence certain misspricings in option markets can be directly related to the premium 0 3 moreover these results extend to american securities which have a third component an additional early exercise premium

taxing capital not a bad idea after all we quantitatively characterize the optimal capital and labor income tax in an overlapping generations model with idiosyncratic uninsurable income shocks and permanent productivity difierences of households the optimal capital income tax rate is signiflcantly positive at 36 percent the optimal progressive labor income tax is roughly a at tax of 23 percent with a deduction of 7 200 relative to average household income of 42 000 the high optimal capital income tax is mainly driven by the life cycle structure of the model whereas the optimal progressivity of the labor income tax is attributable to the insurance and redistribution role of the tax system jel e62 h21 h24

money and credit in liquidity provision abstract this paper studies the liquidity provision in a model where the roles of money are challenged by other financial instruments alternative to money credit can be used as means of payment and rate dominating assets are available to serve as stores of value two features are found to be crucial in rendering money valuable in this environment information asymmetry in credit trading relationship and uncertainty in individuals liquidity demand in general the model economy can display a payment mechanism of money only credit only or mixed use of money and credit in transactions depending on the severity of the information asymmetry the optimal quantity of money in our paper is shown to contrast those in other monetary models

clearly irrational financial market behavior evidence from the early exercise of exchange traded stock options this paper analyzes the early exercise of exchange traded options by different classes of investors over the 1996 to 1999 period a large number of exercises are identified as clearly irrational without invoking any model of market equilibrium customers of discount brokers and customers of full service brokers both engage in a significant number of irrational exercises while traders at large investment houses exhibit no irrational early exercise behavior rational and irrational exercise is triggered for discount and full service customers by the underlying stock price attaining its highest level over the past year and by high returns on the underlying stock it is well known that in the absence of market frictions it is irrational to exercise american call options early except in some circumstances just before the underlying stock goes ex dividend even in the presence of market frictions it is possible to identify without the imposition of any model of market equilibrium call exercises that are clearly irrational in this paper we employ a previously unavailable data set to analyze the rationality of early exercises of chicago board option exchange cboe calls over the 1996 to 1999 period by customers of discount brokers discount customers customers of full service brokers full service customers and traders at large investment houses trading for their firms own accounts firm proprietary traders our first main finding is that there are a large number of early exercises that can be definitively identified as irrational and irrational exercise activity is not evenly distributed across the investor classes discount customers and full ser

time inconsistent preferences and social security in this paper we examine the role of social security in an economy populated by overlapping generations of individuals with time inconsistent preferences who face mortality risk individual income risk and borrowing constraints we find that unfunded social security lowers the capital stock output and consumption for consumers with time consistent or time inconsistent preferences however it may raise or lower welfare depending on the strength of time inconsistency

evaluating natural resource investments notwithstanding impressive advances in the theory of finance over the past 2 decades practical procedures for capital budgeting have evolved only slowly the standard technique which has remained unchanged in essentials since it was originally proposed see dean 1951 bierman and smidt 1960 derives from a simple adaptation of the fisher 1907 model of valuation under certainty under this technique expected cash flows from an investment project are discounted at a rate deemed appropriate to their risk and the resulting present value is compared with the cost of the project this standard textbook technique reflects modern theoretical developments only insofar as estimates of the discount rate may be obtained from crude application of single period asset pricing theory but see brennan 1973 bogue and roll 1974 turnbull 1977 constantinides 1978 the inadequacy of this approach to capital budgeting is widely acknowledged although not widely discussed its obvious deficiency is its the evaluation of mining and other natural resource projects is made particularly difficult by the high degree of uncertainty attaching to output prices it is shown that the techniques of continuous time arbitrage and stochastic control theory may be used not only to value such projects but also to determine the optimal policies for developing managing and abandoning them the approach may be adapted to a wide variety of contexts outside the natural resource sector where uncertainty about future project revenues is a paramount concern

early and late calls of convertible bonds theory and evidence many convertible bonds are called too early or too late relative to the perfect markets decision rule of ingersoll 1977a and ingersoll 1977b we re examine the convertible call decision under corporate taxation and possible default prior to maturity our model predicts that early calls will be associated with high coupon and low call premium dividend income volatility tax rate and interest rate and late calls will be associated with high call premium dividend income tax rate and interest rate and low coupon and volatility these implications are supported by empirical tests carried out with five years of convertible call data

studying optimal paternalism illustrated by a model of sin taxes the classical economic approach to policy analysis assumes that people always respond optimally to the costs and benefits of their available choices a great deal of evidence suggests however that in some contexts people make errors that lead them not to behave in their own best interests economic policy prescriptions might change once we recognize that humans are humanly rational rather than superhumanly rational and in particular it may be fruitful for economists to study the possible advantages of paternalistic policies that help people make better choices we propose an approach for studying optimal paternalism that follows naturally from standard assumptions and methods of economic theory write down assumptions about the distribution of rational and irrational types of agents about the available policy instruments and about the government s information about agents and then investigate which policies achieve the most efficient outcomes in other words economists ought to treat the analysis of optimal paternalism as a mechanism design problem when some agents might be boundedly rational this approach has many advantages first and foremost by explicitly addressing when and how people do and don t pursue their own best interests economists will be better able to contribute to policy debates to contribute to debates over regulating private financial decisions we must study whether financial decisions are based on fallacious statistical reasoning and whether self control problems lead people to borrow too heavily to contribute to debates over teenage smoking we must study whether teenagers become smokers against their long run best interest economists will and should be ignored if we continue to insist that it is axiomatic that constantly trading stocks or accumulating consumer debt or becoming a heroin addict must be optimal for the people doing these things merely because they have chosen to do it a second advantage of our approach is that it forces us to look for the best feasible policy our

is addiction rational theory and evidence this paper makes two contributions to the modeling of addiction first we provide new and convincing evidence that smokers are forward looking in their smoking decisions using state excise tax increases that have been legislatively enacted but are not yet effective and monthly data on consumption second we recognize the strong evidence that preferences with respect to smoking are time inconsistent with individuals both not recognizing the true dife culty of quitting and searching for self control devices to help them quit we develop a new model of addictive behavior that takes as its starting point the standard rational addiction model but incorporates time inconsistent preferences this model also exhibits forward looking behavior but it has strikingly different normative implications in this case optimal government policy should depend not only on the externalities that smokers impose on others but also on the internalities imposed by smokers on themselves we estimate that the optimal tax per pack of cigarettes should be at least one dollar higher under our formulation than in the rational addiction case

the analytic valuation of american options no analytic solutions exists for the valuation of american options written on futures contracts and foreign currencies for which early exercise may be optimal this article formulates the american option valuation problem in economically and mathematically meaningful ways this enables us to derive valuation formulas for american options the properties associated with the optimal exercise boundary are examined and a numerical technique to implement the valuation formulas is presented article published by oxford university press on behalf of the society for financial studies in its journal the review of financial studies

tax incidence when individuals are time inconsistent the case of cigarette excise taxes abstract one of the most cogent criticisms of excise taxes is their regressivity with lower income groups spending a much larger share of their income on goods such as cigarettes than do higher income groups we argue that traditional quantity based measures of incidence are only appropriate under a very restrictive time consistent model of consumption of sin goods a model that is much more consistent with existing evidence on smoking decisions is a time inconsistent formulation where excise taxes on cigarettes serve a self control function that is valued by smokers who would like to quit but cannot this self control function benefits lower income groups more since they have a significantly higher price sensitivity of smoking calibrations show that as a result cigarette taxes are much less regressive than previously assumed and are even progressive for a wide variety of parameter values

how well does the u s social insurance system provide social insurance we analyze the insurance provided by the u s social security and income tax system within a model in which agents receive idiosyncratic wage rate shocks that are privately observed we consider two reforms a piecemeal reform that optimally chooses the social security benefit function and a radical reform that eliminates the entire social insurance system and replaces it with an optimal tax on lifetime earnings the radical reform outperforms the piecemeal reform and achieves nearly all of the maximum possible welfare gain when wages differ permanently over the lifetime when wage shocks match properties in u s data the piecemeal reform outperforms the radical reform

credit mismatch and breakdown abstract this paper studies the phenomenon of mismatch in a decentralized credit market where borrowers and lenders must engage in costly search to establish credit relationships our dynamic general equilibrium framework integrates incentive based informational frictions with a matching process highlighted by i borrowers endogenous market entry and exit decision entry frictions and ii time and resource costs necessary to locate credit opportunities search frictions a key feature of the incentive compatible loan contract negotiated between borrowers and lenders is the interaction of informational frictions in the form of moral hazard with entry and search frictions we find that the removal of entry barriers can eliminate incentive based equilibrium credit rationing more generally entry and incentive frictions are important in understanding the extent of credit rationing and credit mismatch while search and incentive frictions are important for understanding credit market breakdown

the sensitivity of american options to suboptimal exercise strategies the value of american options depends on the exercise policy followed by option holders market frictions risk aversion or a misspecified model for example can result in suboptimal behavior we study the sensitivity of american options to suboptimal exercise strategies we show that this measure is given by the gamma of the american option at the optimal exercise boundary more precisely if b is the optimal exercise price but exercise is either brought forward when or delayed until a price b has been reached the cost of suboptimal exercise is given by b b b 2 where b denotes the american option gamma therefore the cost of suboptimal exercise is second order in the bias of the exercise policy and depends on gamma this result provides new insights on american options

rational prepayment and the valuation of mortgage backed securities this article presents a new model of mortgage prepayments based on rational decisions by mortgage holders these mortgage bolders face beterogeneous transaction costs which are explicitly modeled the model is estimated using a version of hansen s 1982 generalized method of moments and is sbown to capture many of the empirical features of mortgage prepayment estimation results indicate that mortgage holders act as tbougb tbey face transaction costs tbat far exceed tbe explicit costs usually incurred on refinancing they also wait an average of more than a year before refinancing even when it is optimal to do so the model fits observed prepayment behavior as well as thee recent empirical model of schwartz and torous 1989 implications for pricing mortgage backed securities are discussed

a quantitative analysis of capital income taxation this paper studies the quantitative impact of eliminating capital income taxation on capital accumulation and steady state welfare in a general equilibrium model with overlapping generations of sixty five period lived individuals who face idiosyncratic earnings risk borrowing constraints and life span uncertainty under a wide range of parameter configurations the capital income tax rate that maximizes steady state welfare is positive even though eliminating it completely would raise the steady state capital stock toward the golden rule this is because the tax burden is shifted toward the younger and liquidity constrained years reducing the individuals ability to self insure copyright 1998 by economics department of the university of pennsylvania and the osaka university institute of social and economic research association

the cyclical and secular behaviour of the labour input comparing efficiency units and hours worked summary a monthly labour input series designed to correct for the fact that all hours worked are not of the same quality is constructed and its properties compared with unadjusted hours worked this efficiency units series is constructed from bls data on hours worked and earnings by age and sex the cyclical fluctuations displayed by the efficiency units series are smaller on average than those displayed by hours worked although the difference is not large however the secular behaviour of the series is quite different hours worked per capita displays a significant positive trend while efficiency units per capita does not

convertible bonds are not called late starting with ingersoll 1977b the academic literature has repeatedly sought to explain why convertible bonds are called late the findings here demonstrate there is no call delay to explain this paper finds that most convertible bonds given their call protection are called as soon as possible for those that are not there are significant cash flow advantages to delaying the median call delay for all convertible bonds is less than four months if a safety premium is desired to assure the conversion value will exceed the call price at the end of call notice period the median call period is less than a month the question of what is the optimal call policy for convertible bonds has attracted considerable attention since brennan and schwartz 1977 and ingersoll s 1977a seminal work that work suggests that the optimal call policy is to call the bond when the conversion value first exceeds the call price since forcing conversion eliminates the bondholders premium or option value however empirical studies e g ingersoll 1977b and constantinides and grundy 1987 claim that firms consistently deviate from this call policy and delay calls this claim is based on ingersoll s finding that firms wait on average until the conversion value exceeds the call price by 43 9 a result confirmed in mikkelson 1985 trying to explain this call delay phenomenon has generated an impressive literature to date however no one has actually documented whether there is a delay or measured how long the delay is in addition the existing empirical work has focused either on a subsample of called bonds or on a subsample of bonds remaining uncalled at a given point in time these partial samples are not adequate to empirically determine average call delays for convertible bonds or to distinguish between the various hypotheses proposed for call

coexistence of money and interest bearing securities abstract a random matching model with money is used to study the nominal yield on small denomination bearer safe discount securities issued by the government there is always one steady state with matured securities circulating at par and for some parameters another with them circulating at a discount in the former a necessary and sufficient condition for a positive nominal yield on not yet matured securities is exogenous discriminatory treatment of them by the government in the latter the post maturity discount on securities induces a deeper pre maturity discount even without such discriminatory treatment

optimal exercise of executive stock options and implications for firm cost this paper conducts a comprehensive study of the optimal exercise policy for an executive stock option and its implications for option cost average life and alternative valuation concepts the paper is the first to provide analytical results for an executive with general concave utility wealthier or less risk averse executives exercise later and create greater option cost however option cost can decline with volatility we show when there exists a single exercise boundary yet demonstrate the possibility of a split continuation region we also show that for constant relative risk averse utility the option value does not converge to the black and scholes value as the correlation between the stock and the market portfolio converges to one we compare our model s option cost with the modified black and scholes approximation typically used in practice and show that the approximation error can be large or small positive or negative depending on firm characteristics

redistributive taxation in a simple perfect foresight model abstract we investigate the redistributive potential of capital taxation in an intertemporal maximizing model of capital formation first even unanticipated redistributive capital taxation is severely limited in its effectiveness since it depresses wages second under any convergent redistributive tax policy which maximizes a paretian social objective the capital income tax will converge to zero independent of the factor supply elasticities these results are independent of workers holdings of capital

temptation and taxation we study optimal taxation when consumers have temptation and self control problems embedding the class of preferences developed by gul and pesendorfer into a standard macroeconomic setting we first prove in a two period model that the optimal policy is to subsidize savings when consumers are tempted by excessive impatience the savings subsidy improves welfare because it makes succumbing to temptation less attractive we then study an economy with a long but finite horizon which nests as a special case the phelps pollak laibson multiple selves model thereby providing guidance on how to evaluate welfare in this model we prove that when period utility is logarithmic the optimal savings subsidies increase over time for any finite horizon moreover as the horizon grows large the optimal policy prescribes a constant subsidy in contrast to the well known chamley judd result

endogenous market thinness and stock price volatility thin equity markets cannot accommodate temporary bulges of buy or sell orders without large price movements the resulting volatility can induce risk averse transactors who face transaction costs to desert these markets thus thinness and the related price volatility may become joint self perpetuating features of an equity market irrespective of the volatility of asset fundamentals if however appropriate incentive schemes are adopted to encourage entry by additional investors this vicious circle can be broken eventually shifting the market to a selfsustaining superior equilibrium characterized by a higher number of transactors lower price volatility and larger supply of the asset a number of empirical studies cohen et al 1976 telser and higimbotham 1977 pagano 1986 tauchen and pitts 1983 have found that thin speculative markets are ceteris paribus more volatile than deep ones a plausible explanation for this finding is that thin markets are generally characterized by small numbers of transactors per unit time and thus their prices are more sensitive to the impact of individual traders demand shocks conversely in deep markets transactors are so many that the uncorrelated demand shocks experienced by individual traders tend to offset each other and leave market prices largely unaffected while this suggests a rationale for the observed relationship between market size and price volatility it does so by taking market size as the exogenous factor however the volatility of a speculative market may feed back on its size in the sense that the high liquidation risk implied by very volatile prices can induce potential entrants to keep out of the market this paper shows that in a stock market with transaction costs this interaction between thinness and volatility can produce multiple steady state equilibria some characterized by low trade and high volatility and others by high trade and low volatility whether the market will settle in one equilibrium or another depends entirely on the expectations held by economic agents sections 2 and 3 the existence of these multiple bootstrap equilibria can be explained heuristically as follows each additional trader generates a positive externality for other actual or potential traders by decreasing the riskiness of the stock lower risk in turn tends to attract more investors with the effect of raising stock prices and inducing corporations to issue additional equity we thus have a feedback loop between market size and price volatility where market size is measured both along the dimension of the number of traders and along that of the total stock of equities if however investors face transactions costs in the stock market this positive feedback may fail to be operative if the volume of trade is expected to be small investors with relatively high transaction costs will abstain from trading thus the market

from search to match when loan contracts are too long a model of lending is presented where loans are established in matches between banks lenders and entrepreneurs borrowers who meet in a search process projects turn out randomly a quick payoff or a long term payoff that requires a rollover of the loan the model generates under proper parameter conditions two steady states without or with rollover and rollover is socially inefficient under imperfect information the standard debt contract is privately efficient however it extends the domains of equilibria with socially inefficient rollover the global dynamics displays a continuum of equilibrium paths that each exhibits sudden discontinuities crises in which the mass of outstanding loans is reduced by a quantum amount of terminations crises have a cleansing effect

social security and self control preferences abstract we analyze the welfare effects of an unfunded social security system we do so using an overlapping generations economy wherein agents have self control preferences face mortality risk individual income risk and borrowing constraints given our specification of preferences unfunded social security helps reduce the agents temptation to consume in every period consequently the welfare costs it otherwise entails are substantially mitigated while both social security and self control when considered separately reduce welfare their combination renders this effect considerably less severe moreover if the cost of resisting temptation is very high the introduction of social security might even improve welfare

throwing away a billion dollars the cost of suboptimal exercise strategies in the swaptions market abstract this paper studies the costs of applying single factor exercise strategies to american swap options when the term structure is actually driven by multiple factors using a multifactor string market model of the term structure we find that even when single factor models are recalibrated to match the market at every exercise date the exercise strategies they imply can be suboptimal based on estimates of notional amounts outstanding the total present value costs of following single factor strategies could be several billion dollars these results illustrate the importance of using well specified term structure models

measuring self control problems we develop a survey instrument to measure self control problems in a sample of highly educated adults this measure relates in the manner that theory predicts to liquid wealth accumulation and personality measures yet while self control problems are typically seen as resulting in overconsumption and low wealth we identify a significant group who underconsume and thereby accumulate high levels of wealth in addition self control problems are smaller in scale for older than for younger respondents those who put money aside in retirement accounts may be delaying access to a point at which self control problems are no longer important jel d12 d14

pairwise credit in search equilibrium pairwise extension of credit is introduced into the barter search economy previously analyzed by the author the penalty for failure to repay a debt is modeled as the end of trading opportunities since credit availability makes access to trade more valuable there may be multiple equilibrium credit limits since the credit limit affects the implicit interest rate and the stock of inventories it is necessary to check the net impact of the credit limit on the incentive to repay in a calculated example with lumpy credit availability multiple equilibria are very common with a greater credit limit associated with a lower implicit interest rate with smooth credit availability no multiple equilibria were found surprisingly credit can break the no production equilibrium

optimal sin taxes abstract we investigate sin taxes on unhealthy items such as fatty foods that people may by their own reckoning consume too much of we employ a standard optimal taxation framework but replace the standard assumption that all consumers have 100 self control with an assumption that some consumers may have some degree of self control problems we show that imposing taxes on unhealthy items and returning the proceeds to consumers can generally improve total social surplus because such taxes counteract over consumption by consumers with self control problems while at the same time they naturally redistribute income to consumers with no self control problems who consume less such taxes can even create pareto improvements finally we demonstrate with some simple numerical examples that even if the population exhibits relatively few self control problems optimal taxes can still be large

measuring self control problems a structural estimation we perform a structural estimation of the preference parameters in a buffer stock consumption model augmented with temptation disutility we adopt a two stage method of simulated moments methodology to match our simulated moments with those observed in the us survey of consumer finances to identify the parameters we use liquid and quasi liquid retirement wealth holdings at different ages as target moments we find evidence of a significantly positive degree of temptation and estimates under the unrestricted model are more precise than estimates under the restricted model with no temptation overall a model with temptation preferences explains better the observed target moments

the suspension of borrowing an implicit penalty for loan default under imperfect information abstracta credit seeker may be suspended from borrowing for a period of time due to a previous default such suspension is widely used in bank lending through credit check our work analyses the effects of suspension on the investment choice of borrowers under uncertainty and on the lending policy of banks facing asymmetric information we show that suspension should be tightened at low loan rates but loosened otherwise to improve the repayment performance of borrowers we also show that although credit rationing may not be completely removed due to imperfect information the excess demand for credit or transitive waiting in the market can actually be attenuated by such efficient use of suspension our theoretical predictions are consistent with observed cyclical patterns of changes in lendingrates and suspension severity

on the suboptimality of single factor exercise strategies for bermudan swaptions abstract this paper resolves the disagreement between longstaff et al 2001 journal of finance economics 62 39 66 and andersen and andreasen 2001 journal of financial economics 62 3 37 over the effectiveness of the common business practice of using best fit single factor term structure models to deduce exercise strategies of bermudan swaptions i examine the cost of using recalibrated single factor models to determine the exercise strategy for bermudan swaptions in a multifactor world i show that single factor exercise strategies applied in a multifactor world only give rise to economically insignificant losses furthermore i find that the conditional model risk as defined in longstaff et al 2001 journal of finance economics 62 39 66 is statistically insignificant given the number of observations additional tests using the primal dual algorithm of andersen and broadie 2004 management science 50 9 indicate that losses found in longstaff et al 2001 journal of finance economics 62 39 66 cannot as claimed be ascribed to the number of factors

the macroeconomics of labor and credit market imperfections labour market frictions are not the only possible source of high unemployment credit market imperfections driven by microeconomic frictions and influenced by macroeconomic factors could also be to blame to develop this idea in a simple and tractable macroeconomic model we treat credit and labour market imperfections in a symmetrical way accordingly we introduce specificity in credit relationships and assume that credit to potential entrepreneurs is rationed due to endogenous search frictions in the spirit of diamond 1990 these imperfections mirror job search frictions in the labour market we study the determination of equilibrium unemployment in the presence of credit market frictions both with exogenous and endogenous wages we explore a number of possible extensions endogenous destruction monetary policy and the short run effects of financial liberalization

social security reform with self control preferences abstract this paper analyzes a fully funded social security system under the assumption that agents face temptation issues agents are required to save through individually managed personal security accounts without and with mandatory annuitization when the analysis is restricted to crra preferences our results are congruent with the literature in indicating that the complete elimination of social security is among the reform scenarios that maximize welfare however when self control preferences are introduced and as the intensity of self control becomes progressively more severe the social security elimination scenario loses ground very rapidly in fact in the case of relatively severe temptation the elimination of social security becomes the least desirable alternative under the light of the above findings any reform proposal regarding the social security system should consider departures from standard preferences to preference specifications suitable for dealing with preference reversals

the rationality of early exercise decisions evidence from the s p 100 index options market this study provides a comprehensive empirical analysis of the early exercise bistoty of sp but we show that a substantal number of these decisions are clearly irratonal since it would bave been possible to realize a larger riskless net cash jlow by seuling unlike p us studies of early exercise our tests of efflciency and the rationat decions tbatpresumably lead to eficient markets are model independet we also provide evidence concerning the relatve significance of dividends and the wild card to index optonpricing models and introduce and document the importance of the opton to exercise and avoid the indirect costs oftbe spread we alsofind evidence of a significant day of tbe week exercise effect and present some likely explanations for that effect

consumption savings decisions with quasi geometric discounting we study the consumption savings problem of an infinitely lived rational consumer who has time inconsistent preferences in the form of quasi geometric discounting the consumer operates a weakly concave production function and must simply divide current resources into current consumption and savings there is no uncertainty a solution to the consumer s problem is a subgame perfect equilibrium of a dynamic game between the consumer s successive selves we show that this game has a continuum of equilibria in stationary markov strategies not only is the stationary point of the consumer s asset holdings indeterminate but each stationary point has a continuum of dynamic paths converging to it the savings policy rules underlying these dynamic paths are step functions

heterogeneous borrowers liquidity and the search for credit abstract we develop a general equilibrium model of credit formation where borrowers and lenders must search for matches and where the composition of borrowers adjusts to satisfy equilibrium entry conditions when market liquidity dries up as a result of fundamental shocks to the system fewer borrowers will participate in the credit market with low quality borrowers suffering disproportionately because of a flight to quality however less liquid credit markets need not be associated with lower social output because the effect of higher average quality may outweigh that of reduced market participation depending crucially on the source of the liquidity shock

a model of pairwise credit a model of credit as a pairwise activity is studied in a random matching model where there are no social sanction mechanisms the model depicts some prevalent features of credit arrangements even though there are no informational asymmetries and the price of credit is determined competitively there is credit rationing the credit relationships are also longlasting the introduction of credit into a barter economy does not necessarily increase the welfare of debtors

employee stock option exercises an empirical analysis this paper describes the exercise behavior of over 50 000 employees who hold longterm options on employer stock at eight corporations employees typically exercise options years before expiration commonly sacrificing half of the black scholes value exercise is strongly associated with recent stock price movements the market to strike ratio proximity to vesting dates time to maturity volatility and the employee s level within the company these findings have implications for compensation planners the fasb as it develops a new accounting standard for options and financial statement users and preparers who apply and interpret the new fasb standard

rational expectations business cycles in search equilibrium we examine the rational expectations equilibrium paths of the model of search and barter in diamond s aggregate demand management in search equilibrium for some initial positions there are two equilibrium paths converging to different steady states with the high activity path pareto dominating the low activity path with some parameters there is also a continuum of equilibrium paths converging to another steady state moreover there can be cycles that are equilibrium paths even though the environment is stationary

data breaches and identity theft abstract an environment is analyzed in which agents join clubs payment networks in order to facilitate trade the networks compile personal identifying data pid so as to match transactors to transactions histories technological limitations cause the networks data management practices to impact each other s incidence and costs of identity theft too much data collection and too little security arise in equilibrium with noncooperative networks compared to the efficient allocation a number of potential remedies are analyzed 1 reallocations of data breach costs 2 mandated security levels and 3 mandated limits on the amount of data collected

self control and the theory of consumption to study the behavior of agents who are susceptible to temptation in infinite horizon consumption problems under uncertainty we define and characterize dynamic self control dsc preferences dsc preferences are recursive and separable in economies with dsc agents equilibria exist but may be inefficient in such equilibria steady state consumption is independent of initial endowments and increases in self control increasing the preference for commitment while keeping self control constant increases the equity premium removing nonbinding constraints changes equilibrium allocations and prices debt contracts can be sustained even if the only feasible punishment for default is the termination of the contract

credit and money in a search model with divisible commodities this paper examines the competition between money and credit in a search model with divisible commodities it is shown that fiat money can be valuable even though it yields a lower rate of return than the coexisting credit the competition between money and credit increases efficiency the monetary equilibrium with credit pareto dominates the monetary equilibrium without credit whenever the two coexist when a credit is repaid with money the competition also bounds the purchasing power of money from below by that of credit and so eliminates the weak inefficient monetary equilibrium found in previous search models with numerical examples three different monetary equilibria are ranked and the properties of the interest rate are examined

optimal taxation of capital income in general equilibrium with infinite lives this paper analyzes the optimal tax on capital income in general equilibrium models of the second best agents have infinite lives and utility functions which are extensions from the koopmans form the population is heterogeneous the important property of the models is the equality between the social and the private discount rates in the long run i find that the optimal tax rate is zero in the long run for a special case of additively separable utility functions i then determine the tax rates along the dynamic path and conditions that are sufficient for the local stability of the steady state

the implication of missing the optimal exercise time of an american option the optimal exercise policy of an american option dictates when the option should be exercised in this paper we consider the implications of missing the optimal exercise time of an american option for the put option this means holding the option until it is deeper in the money when the optimal decision would have been to exercise instead we derive an upper bound on the maximum possible loss incurred by such an option holder this upper bound requires no knowledge of the optimal exercise policy or true price function this upper bound is a function of only the option holder s exercise strategy and the intrinsic value of the option we show that this result holds true for both put and call options under a variety of market models ranging from the simple black scholes model to complex stochastic volatility jump diffusion models numerical illustrations of this result are provided we then use this result to study numerically how the cost of delaying exercise varies across market models and call and put options we also use this result as a tool to numerically investigate the relation between an option holder s risk preference levels and the maximum possible loss he may incur when adopting a target payoff policy that is a function of his risk preference level

the sensitivity of tests of the intertemporal allocation of consumption to near rational alternatives suppose a consumer sets consumption equal to income each period rather than following the optimal permanent income decision rule how much utility does he lose this paper finds that the answer is typically less than 10 cents 1 per quarter in environments specified by popular tests on aggregate data it includes calculations of the costs of excess sensitivity and excess smoothness to income and interest rate changes and the costs of ignoring information it concludes that the theory does not make predictions for aggregate tests that are robust to small costs such as information or transactions copyright 1989 by american economic association

the computational experiment an econometric tool an economic experiment consists of the act of placing people in an environment desired by the experimenter who then records the time paths of their economic behavior performing experiments that use actual people at the level of national economies is obviously not practical but constructing a model economy and computing the economic behavior of the model s people is such experiments are termed computational this essay specifies the steps in designing a computational experiment to address some well posed quantitative question the authors emphasize that the computational experiment is an econometric tool used in the task of deriving the quantitative implications of theory

robust pricing of the american put option a note on richardson extrapolation and the early exercise premium this paper presents a detailed analysis of the numerical implementation of the american put option decomposition into an equivalent european option plus an early exercise premium kim 1990 jacka 1991 carr et al 1992 it subsequently introduces a new algorithm based upon this decomposition and richardson extrapolation this new algorithm is based upon a the derivation of the correct order for the error term when applying richardson extrapolation which is used to control the error of the extrapolated prices b an innovative adjustment of kim s 1990 discrete time early exercise premium so that these premiums monotonically converge and therefore it is appropriate to use them in extrapolation and c the optimal exercise frontier can be quickly computed through newton s method permitting the efficient implementation of the decomposition formula in practice numerical experiments show that this new algorithm is accurate efficient easy to implement and competitive in comparison with other methods finally it can also be applied to other american exotic securities

temptation driven behavior and taxation a quantitative analysis in a life cycle model i introduction a central research question in the dynamic fiscal policy literature during the last 30 years or so is whether under fairly general modeling choices the government should impose a positive tax on capital income in the long run the original answer to this question is negative and is due to the seminal papers by chamley 1986 and judd 1985 who established that in the context of a standard neoclassical growth model with infinitely lived individuals an optimal income tax policy entails taxing capital at confiscatory rates in the short run and setting capital income taxes equal to zero in the long run only labor income should be taxed in the long run since then several modeling choices that cast doubt on the validity of this result were identified in the literature imrohoroglu 1998 showed that the optimal capital income tax rate is strictly positive in an overlapping generations olg setting where individuals face idiosyncratic earnings risk borrowing constraints and life span uncertainty conesa kitao and krueger 2009 extended imrohoroglu 1998 by adding a labor leisure choice they demonstrated that the optimal capital income tax rate is equal to 36 and concluded that this high rate is mainly driven by the life cycle structure of the model in contrast krusell kuruscu and smith 2010 analytically showed that within a class of ramsey tax schemes the optimal capital income tax rate should be negative that is savings should be subsidized when agents have self control problems moreover in the special case where consumers succumb completely to temptation ramsey taxes deliver first best welfare outcomes and in contrast to the chamley judd result the optimum calls for a subsidy to savings however an integrated assessment of the combined effects of the relevant trade offs both along the dimension of differences in preferences and along the dimension of the scope of capital income taxation versus labor income taxation is missing from all previous studies in both social security and capital taxation literature and this paper aims to bridge the gap in the literature and contribute in this aspect to the best of our knowledge this paper is the first study that introduces temptation driven preferences in a quantitative model aiming to tackle the question on the optimal capital income tax before proceeding to specifically articulate this paper s contribution to the literature we consider critical to address a question that lies at the very core of our line of research namely why fiscal policy models with time inconsistent or self control preferences are relevant in the first place initially the literature pioneered by strotz 1956 and phelps and poliak 1968 corroborated evidence coming from both introspection and experiments that agents exhibit preference reversals as time passes different strands within this literature have suggested that these preference reversals could be induced by either time inconsistent preferences see laibson 1997 or self control preferences gul and pesendorfer 2004 time inconsistent preferences typically assume that agents have sequences of different selves each valuing consumption streams in a unique way in contrast gul and pesendorfer 2004 provide a dynamically consistent model suitable for addressing preference reversals that does not necessitate splitting up the consumer in multiple selves that is self control preferences these preferences describe an individual that in every period is tempted to consume his entire endowment when he consumes less than his endowment he incurs a disutility cost that stems from exercising self control that is self control cost optimal behavior trades off the temptation to consume vis a vis the long run self interest of the individual 1 alongside these theoretical underpinnings there is sound empirical and experimental evidence that agents suffer from self control problems

indivisibilities lotteries and monetary exchange we introduce lotteries randomized trading into search theoretic models of money in a model with indivisible goods and fiat money we show goods trade with probability 1 and money trades with probability where 1 iff buyers have sufficient bargaining power with divisible goods a nonrandom quantity q trades with probability 1 and again money trades with probability where 1 iff buyers have sufficient bargaining power moreover q never exceeds the efficient quantity not true without lotteries we consider several extensions designed to get commodities as well as money to trade with probability less than 1 and to illuminate the efficiency role of lotteries