saddlepoint approximations for affine jump diffusion models abstract affine jump diffusion ajd processes constitute a large and widely used class of continuous time asset pricing models that balance tractability and flexibility in matching market data the prices of e g bonds options and other assets in ajd models are given by extended pricing transforms that have an exponential affine form these transforms have been characterized in great generality by duffie et al 2000 transform analysis and asset pricing for affine jump diffusions econometrica 68 1343 1376 calculating model prices requires inversion of these transforms and this has limited the application of ajd models to the comparatively small subclass for which the transforms are available in closed form this article seeks to widen the scope of ajd models amenable to practical application through approximate transform inversion techniques more specifically we develop the use of saddlepoint approximations for ajd models these approximations facilitate the calculation of prices in ajd models whose transforms are not available explicitly we derive and test several alternative saddlepoint approximations and find that they produce accurate prices over a wide range of parameters

the non dynamic equivalence of monetary and exchange rate rules under imperfect capital mobility and rational expectations abstract in the present paper we introduce a model in which the dynamic adjustment of the real exchange rate and other real variables depends on whether the economy follows a monetary or an exchange rate rule this result stands in opposition to the monetarist models of the open economy where there is a dynamic equivalence between the two rules

collusion and overlending i introduction for a long time have korean companies been engaged in unbridled expansionism financed through loans inefficient octopus style management and over and duplicate investment thus expediting the structural failure of the economy this failure to concentrate on profits consolidation and efficiency provided the fuse to the bankruptcy bombs that triggered the foreign exchange and economic crises the collusion between the conglomerates financial sector and politicians made this financial monopoly possible chosun ilbo december 26 1997 collusion and overlending in the korean financial sector may be best illustrated by the above editorial highlight of chosun ilbo the most read newspaper in korea its 1997 financial crisis is primarily triggered by continual bankruptcies of chaebols conglomerates which with assistance from politicians had borrowed heavily from financial institutions in financing their investment projects 1 unlike some other asian countries experiencing problems in their financial sector due to shifts in investment projects toward real estates such as japan hong kong and thailand chaebols in korea concentrated mostly on manufacturing activities 2 in this study we establish a tractable model of overlending with three key players namely chaebols financial institutions and politicians as highlighted in chosun ilbo the model is designed to achieve two primary goals that are crucial for matching some key observations during the korean turmoil first we illustrate how overlending can be an equilibrium outcome with collusion between chaebols and politicians when the economic environment is favorable this occurs despite that such a collusion distorts normal borrowing lending operation by causing a discernible shift in loan composition from more to less productive investment projects second we show that as the economic environment gradually deteriorates there can be a shift from a collusion to a no collusion equilibrium the combination of deterioration in fundamentals and expectations of an equilibrium shift can trigger economy wide financial crisis more specifically we construct a simple principal supervisor agent model of corruption and overlending the principal is the formal authority of loan decision making of a financial institution or in short the financial institution the supervisor is a politician who serves as the informational intermediary in the borrowing lending arrangement via his her connections and networking 3 the agent is a chaebol of an unknown type which seeks for external financing of a set of risky projects a politician s favorable signal about the borrowing chaebol s overall performance would grant the approval of the loan to finance an array of risky projects whose returns depend on idiosyncratic shocks that cannot be washed out in aggregation within the chaebol as an outside alternative to making the loan the financial institution can invest in the world capital market where a fixed rate of return is guaranteed this portfolio decision depends on a comparison of the expected average returns on the given set of risky projects with the safe returns on investments in the world capital market while both the chaebol s type and the state of nature are unobservable to the financial institution we for simplicity assume that politician s connections and networking can fully uncover the true type of the chaebol this valuable information possessed by the politician is one that the financial institution has an incentive to purchase but a low type chaebol has an incentive to conceal whether the politician ends up revealing truthfully this information depends on how much to obtain from the lender in terms of general support versus how much to gain from the borrower in terms of bribes or side payments when a low type chaebol has the politician on its side information is distorted and a collusion equilibrium arises

collapsing exchange rate regimes and exchange rate dynamics some further examples abstract this paper extends some recent perfect foresight models of balance of payments crises and exchange rate realignments to a world of smart speculators sticky prices and restricted international capital movements the likelihood and timing of a regime collapse are shown to depend upon initial foreign reserve endowments monitary policy speeds of market adjustment and future exchange rate policy these factors are also shown to influence the dynamic behavior of the exchange rate and prices during a transitional period of floating

the politics of speculative attacks in industrial democracies recent models of speculative currency crises contend that market expectations of policy behavior can trigger a speculative attack we argue that political processes and partisan objectives inform expectations about the government s commitment to the exchange rate first market actors anticipate periods when the partisan identity of a government may change through an election or a cabinet collapse second party labels provide information to currency traders about the policy objectives of a potential government consequently we contend that the probability of a speculative attack will be higher when markets expect the cabinet to end and when the cabinet dissolution is likely to produce a leftward shift in policy a discrete timesurvival model is used to estimate the probability that a cabinet will dissolve in any given month for sixteen parliamentary democracies from 1970 to 1995 the predicted values are then used as a proxy for market expectations in a model of speculative currency crises

capital controls and balance of payments crises abstract the theory of balance of payments crises shows that under perfect foresight a system of fixed exchange rate is not sustainable in the presence of diverging economic policies in this paper it is shown how and why capital controls succeed in maintaining the principle of a fixed but adjustable parity both cases of a devaluation and a revaluation are considered and a condition for a parity change to be credible is presented

balance of payments crises and devaluation the collapse of a fixed exchange rate is typically marked by a sudden balance of payments crisis in which speculators fleeing from the domestic currency acquire a large portion of the central bank s foreign exchange holdings faced with such an attack the central bank often withdraws temporarily from the foreign exchange market allowing the exchange rate to float freely before devaluing and returning to a fixed rate regime this paper links the timing of the initial speculative attack to the magnitude of the expected devaluation and to the length of the transitional period off loating an implication of the analysis is that there exist devaluations so sharp and transition periods so short that acrisis must occur the moment the market first learns that the current exchange parity will eventually be altered for sufficiently long transition periods the floating exchange rate overshoots its new peg before appreciating back toward it for shorter periods the rate depreciates monotonically to its new fixed level accordingly the central bank s return tothe foreign exchange market can occasion a capital outflow or a capital inflow this abstract was borrowed from another version of this item

speculative currency attacks and balance of payments crises abstract this paper reviews the recent theoretical literature on collapsing exchange rate regimes using a combination of technique intuition and realworld observation we discuss the literature s main insights point out some unresolved questions and offer suggestions for future research the survey should be of interest to both specialists and non specialists in the field of international macroeconomics

fast delta computations in the swap rate market model abstract we develop an efficient algorithm to implement the adjoint method that computes sensitivities of an interest rate derivative to different underlying rates in the co terminal swap rate market model the order of computation per step of the new method is shown to be proportional to the number of rates times the number of factors which is the same as the order in the libor market model

a flexible matrix libor model with smiles abstract we present a flexible approach for the valuation of interest rate derivatives based on affine processes we extend the methodology proposed in keller ressel et al in press by changing the choice of the state space we provide semi closed form solutions for the pricing of caps and floors we then show that it is possible to price swaptions in this multifactor setting with a good degree of analytical tractability this is done via the edgeworth expansion approach developed in collin dufresne and goldstein 2002 a numerical exercise illustrates the flexibility of wishart libor model in describing the movements of the implied volatility surface

collapsing exchange rate regimes another linear example abstract in the literature on speculative attacks on a fixed exchange rate it is usually assumed that the monetary authority responsible for fixing the rate reacts passively to the monetary disruption caused by the attack this assumption is grossly at odds with actual experience where the monetary base implications of the attacks are usually sterilized such sterilization means that the attack is no longer exclusively a monetary event and requires that the standard attack model be broadened to include the effects of sterilization on other markets these issues are motivated by reference to the december 1994 collapse of the mexican peso

a bio economic model of community incentives for wildlife management under campfire this paper formulates a bio economic model to analyze community incentives for wildlife management under benefit sharing programs like the communal areas management programme for indigenous resources campfire in zimbabwe three agents influence the wildlife stock a parks agency determines hunting quotas outside poachers hunt illegally and a local community may choose to protect wildlife by discouraging poaching wildlife generates revenues from hunting licenses and tourism it also intrudes on local agriculture we consider two benefit sharing regimes shares of wildlife tourism rents and shares of hunting licenses resource sharing does not necessarily improve community welfare or incentives for wildlife conservation results depend on the exact design of the benefit shares the size of the benefits compared with agricultural losses and the way in which the parks agency manages hunting quotas

ruling out divergent speculative bubbles abstract the growth in the empirical literature on testing for divergent in mean speculative bubbles indicates that existing theoretical arguments for ruling out such price paths are not sufficiently compelling here we strengthen the case for ruling out explosive or implosive bubbles a priori by filling in two gaps first we demonstrate why divergent stochastic bubbles arising from purely extrinsic uncertainty as in blanchard 1979 cannot be equilibria in a monetary optimizing model second we show why existing arguments for ruling out implosive price bubbles are insufficient in some cases and we provide stronger arguments

a review of the stern review on the economics of climate change the stern review calls for immediate decisive action to stabilize greenhouse gases because the benefits of strong early action on climate change outweighs the costs the economic analysis supporting this conclusion consists mostly of two basic strands the first strand is a formal aggregative model that relies for its conclusions primari ly upon imposing a very low discount rate concerning this discount rate aspect i am skeptical of the review s formal analysis but this essay points out that we are actual ly a lot less sure about what interest rate should be used for discounting climate change than is commonly acknowledged the review s second basic strand is a more intuitive argument that it might be very important to avoid possibly large uncertain ties that are difficult to quantify concerning this uncertainty aspect i argue that it might be recast into sound analytical reasoning that might justify some of the review s conclusions the basic issue here is that spending money to slow global warming should perhaps not be conceptualized primarily as being about consump tion smoothing as much as being about how much insurance to buy to offset the small change of a ruinous catastrophe that is difficult to compensate by ordinary savings

gold monetization and gold discipline gold and its price have emerged as frequent topics of both academic and government debate 2 public attention focused on the gold market since gold s price began fluctuating violently in 1980 and 1981 has turned to gold as a possible means of removing some discretion inherent in the current fiat money system since lack of adherence to monetary rules can lead to problems of dynamic policy inconsistency academic economists have begun seriously to reconsider monetary standards based either on gold or on some other commodity as politically feasible methods of establishing rules 3

a theory of the nominal term structure of interest rates a model of the nominal term structure of interest rates is developed that has a positive and stationary process for the interest rate and delivers closed form expressions for the prices of discount bonds and european options on bonds unlike the one state variable version of the cox ingersoll and ross 1985 model this model even in its one state variable version allows the term premium to change sign as a function of the state and the term to maturity and also allows for shapes of the yield curve that are observed in the u s data but that are disallowed in the cox ingersoll and ross model article published by oxford university press on behalf of the society for financial studies in its journal the review of financial studies

conservation and human welfare economic analysis of ecosystem services the importance of the links between well functioning ecosystems and human well being are clearly evident in our age of rapidly changing environmental and socio economic conditions and yet the role ecosystems play in supporting and sustaining human welfare has been only a marginal area of study to date in the field of economics dasgupta 2010 but this is starting to change millennium ecosystem assessment 2005 and the burgeoning literature on ecosystem services that has followed largely instigated by work in ecology has begun to percolate into economics the number of articles by economists on various aspects of ecosystem services including the benefits of conserving ecosystems and biodiversity tradeoffs among services payments for ecosystem services pes and other incentive mechanisms has risen dramatically in the past several years still the economics literature on ecosystems and biodiversity is nowhere near as prominent as the economics literature on climate change economists have played a central role in defining the key elements of the debate on climate change following publication of the stern review stern 2007 and the ensuing debates e g nordhaus 2007 sterner and persson 2008 weitzman 2007 economists have yet to play such a central role in ecosystem services and biodiversity ecosystems provide a wide range of benefits from the water and climate regulation roles of forests the waste assimilation and storm regulation capacities of wetlands to the cultural and aesthetic benefits derived from savannas ecosystems processes and raw materials are

20th anniversary of eaere the european association of environmental and resource economists environmental and resource economics occupies a curious place in contemporary economics i know of no economist who does not regard nature to be a vital capital asset nor do i know any economist who does not regard humanity s dealings with nature to involve inter temporal externalities and yet most economists appear to be convinced that technological advances and the accumulation of reproducible capital and growth in human capital can overcome diminutions in natural capital otherwise it is hard to explain why twentieth century economics has been so detached from the environmental sciences judging by the profession s writings we economists see nature when we see it at all as a backdrop from which resources and services can be drawn in isolation macroeconomic forecasts routinely exclude natural capital and accounting for nature if it comes into the calculus at all is an afterthought to the real business of doing economics when asked economists acknowledge nature s existence but many deny she is worth much at the margin i have heard professional colleagues remark at seminars that the services nature provides amount at best to 2 3 of an economy s output which is the share of agriculture in the gross domestic product of the united states why they ask should one incorporate a capital asset in macro economic models of growth and distribution when it is of negligible importance typically growth models assume that nature is a fixed indestructible factor of production 1 the problem with the assumption is that it is wrong nature consists of degradable resources agricultural land forests watersheds fisheries fresh water sources wetlands the atmosphere more generally ecosystems are assets that are self regenerative but suffer from depletion or deterioration when they are over used 2 the innumerable processes that characterize nature run at different speeds and operate at different spatial scales which give rise to positive feedback loops that unless countered can mean catastrophes for people ranging from village communities to populations covering entire biomes moreover the environmental sciences tell us that the elasticity of substitution between reproducible capital and

the vulnerability of price stabilization schemes to speculative attack this paper examines the effects of government attempts to stabilize the prices of commodities by use of buffer stocks agricultural goods subject to supply uncertainty as well as depletable resources are considered in each case it is shown that the resulting rational expectations competitive equilibrium contains a speculative attack a situation where the entire government stock is suddenly purchased by previously inactive speculators the analysis is applied to the historical attempt to peg the gold price which caused the attack of 1968 the insights gained and the methodology developed also apply to the various international agreements to impose bans on commodity prices which have been proposed by the united nations conference on trade and development

speculative attack and the external constraint in a maximizing model of the balance of payments balance of payments models of speculative attack differ from non renewable resource models in that foreign exchange reserves may be borrowed from abroad this paper shows that in an idealized world where all private income is subject to lump sum taxation central bank reserves can become infinitely negative without violating the government s intertemporal budget constraint none the less a growth rate of domestic credit exceeding the world interest rate if maintained indefinitely leads to violation of the constraint in the paper s model given an assumed limit to official external borrowing the paper next analyses inevitable transitions between fixed and floating exchange rate regimes when individual preferences are explicitly specified in a discrete time deterministic model the collapse of a fixed rate may be characterized by two successive speculative attacks

rational and self fulfilling balance of payments crises speculative attacks on a pegged exchange rate must sometimes occur ifasset price paths are to be free of abnormal profit opportunities suchattacks are fully rational as they reflect the market s response to aregime breakdown that is inevitable the authors shows that under someexpectations about policy balance of payments crises can also be purely self fulfilling events in such cases even a permanently viableregime may collapse and the economy will possess multiple equilibriacorresponding to different subjective assessments of the probability ofa crisis the behavior of the domestic interest rate will naturally reflect the possibility of a speculative attack copyright 1986 by american economic association

an exact bond option formula this paper derives a closed form solution for european options on pure discount bonds assuming a mean reverting gaussian interest rate model as in vasicek 8 the formula is extended to european options on discount bond portfolios

option pricing where the underlying assets follow a gram charlier density of arbitrary order abstract if a probability distribution is sufficiently close to a normal distribution its density can be approximated by a gram charlier series a expansion in option pricing this has been used to fit risk neutral asset price distributions to the implied volatility smile ensuring an arbitrage free interpolation of implied volatilities across exercise prices however the existing literature is restricted to truncating the series expansion after the fourth moment this paper presents an option pricing formula in terms of the full untruncated series and discusses a fitting algorithm which ensures that a series truncated at a moment of arbitrary order represents a valid probability density while it is well known that valid densities resulting from truncated gram charlier series a expansions do not always have sufficient flexibility to fit all market observed option prices perfectly this paper demonstrates that option pricing in a model based on these densities is as tractable as the far less flexible original model of black and scholes 1973 allowing non trivial higher moments such as skewness excess kurtosis and so on to be incorporated into the pricing of exotic options generalising the gram charlier series a approach to the multiperiod multivariate case a model calibrated to standard option prices is developed in which a large class of exotic payoffs can be priced in closed form furthermore this approach when applied to a foreign exchange option market involving several currencies can be used to ensure that the volatility smiles for options on the cross exchange rate are constructed in a consistent arbitrage free manner

the international monetary system forty years after bretton woods review essay in may 1984 a distinguished group of central bankers and economists gathered for a conference at bretton woods to consider the evolution of the world monetary system that was born at that location forty years earlier this volume contains nine essays with accompanying discussion on issues of performance and reform of current international monetary arrangements these papers deal with problems facing the industrialized and the lessdeveloped countries and assess the institutions that have been set up to accommodate these problems the major accomplishments of the original bretton woods conference were of course the establishment of the system of payments based on fixed exchange rates and the organization of the world bank and the international monetary fund as the order developed in the late 40 s and early 50 s each central bank saw it as its duty to intervene in foreign exchange markets to ensure an essentially fixed parity of their currency with respect to the dollar the role of the u s was to guarantee the dollar price of gold at 35 an ounce the system has been called a dollar standard because the dollar played the role of a reserve currency one of the paradoxes of the system as robert triffin pointed out in the early 60 s is that in order to produce a continuing and rapid enough expansion of world reserves the u s had to run balance of payments deficits yet continued deficits by the u s threatened the convertibility of the dollar into gold as it happened the system of fixed parities broke down in the early 70 s not because of a lack of reserves but because a glut of dollars made the bretton woods dollar exchange rates untenable the system eventually evolved into one in which most of the industrialized countries currencies more or less are determined by the market while the currencies of most second and third world countries are pegged to a major currency the floating period has been

closed form solutions for term structure derivatives with log normal interest rates we derive a unified model that gives closed form solutions for caps and floors written on interest rates as well as puts and calls written on zero coupon bonds the crucial assumption is that simple interest rates over a fixed finite period that matches the contract which we want to price are log normally distributed moreover this assumption is shown to be consistent with the heath jarrow morton model for a specific choice of volatility closed form solutions for interest rate derivatives in particular caps floors and bond options have been obtained by a number of authors for markovian term structure models with normally distributed interest rates or alternatively log normally distributed bond prices see for example jamshidian 1989 1991a heath jarrow and morton 1992 brace and musiela 1994 geman el karoui and rochet 1995 these models support black scholes type formulas most frequently used by practitioners for pricing bond options and swaptions unfortunately these models imply negative interest rates with positive probabilities and hence they are not arbitrage free in an economy with opportunities for riskless and costless storage of money briys crouhy and schobel 1991 apply the gaussian framework to derive closed form solutions for caps floors and european zero coupon bond options to exclude the influence of negative forward rates on the pricing of zero coupon bond options they introduce an additional boundary condition as shown by rady and sandmann 1994 these pricing formulas are only supported by a term structure model with an absorbing boundary for the forward rate at zero where the absorbing probability is not negligible which for a term structure model is a quite problematic assumption

diversity productivity and temporal stability in the economies of humans and nature abstract recent advances in ecology are of great potential relevance to economists here we present two ecological models of mechanisms of competition and coexistence and use these to derive how the primary productivity of ecosystems the amount of carbon dioxide removed from the atmosphere and stored by plants the efficiency of resource use and the spatial and temporal variability of productivity and resource use should depend on diversity we then discuss the relevance of these results to 1 ecosystem services and the economic value of diversity and 2 the functioning of any competitive system including the economy

collapsing exchange rate regimes some linear examples abstract we construct a pair of linear examples to study the collapse time of a fixed exchange rate regime the first example is a perfect foresight continuous time model which allows calculation of the exact collapse time and the tracking of reserves the second example is a discrete time stochastic model which yields an endogenous probability distribution over the collapse time and produces a forward discount of the exchange rate

the exact timing of the collapse of an exchange rate regime and its impact on the relative price of traded goods as of february 28 1983 ninety four countries are classified as having a fixed exchange rate regime 38 are pegged to the u s dollar 13 to the french franc 14 to the special drawing right and 24 to different baskets of currencies the choice of a fixed exchange rate peg implies a specific monetary discipline namely monetary growth equal to the growth rate of the currency or currencies to which a country is pegged monetary policy is thus subject to an exchange rate rule rather than to either a monetary growth rule or alternatively to discretionary policy a fixed exchange rate is a specific case of an active crawling peg where the preannounced rate of change in the exchange rate is zero active crawling peg rules whereby the exchange rate is adjusted downward by a preannounced amount over a specified period of time have been practiced in various places particularly in latin america recent experiments include argentina beginning december 1978 brazil during the 1980 calendar year chile from february 1978 to june 1979 jamaica from may 1978 to may 1979 portugal from august 1977 to june 1979 and uruguay beginning october 1978 1 at times the prean

derivative pricing with wishart multivariate stochastic volatility this paper deals with the pricing of derivatives written on several underlying assets or factors satisfying a multivariate model with wishart stochastic volatility matrix this multivariate stochastic volatility model leads to a closed form solution for the conditional laplace transform and quasi explicit solutions for derivative prices written on more than one asset or underlying factor two examples are presented i a multiasset extension of the stochastic volatility model introduced by heston 1993 and ii a model for credit risk analysis that extends the model of merton 1974 to a framework with stochastic firm liability stochastic volatility and several firms a bivariate version of the stochastic volatility model is estimated using stock prices and moment conditions derived from the joint unconditional laplace transform of the stock returns

capital mobility and exchange rate overshooting abstract this paper examines the relation between the degree of capital mobility and the exchange rate overshooting phenomenon in a framework that employs a stock formulation of the capital account the results are compared with those emerging from the corresponding flow formulation and it is shown that the stock formulation modifies the quantitative but not qualitative implications of the model

a review of the stern review on the economics of climate change how much and how fast should we react to the threat of global warming the stern review argues that the damages from climate change are large and that nations should undertake sharp and immediate reductions in greenhouse gas emissions an examination of the review s radical revision of the economics of climate change finds however that it depends decisively on the assumption of a near zero time discount rate combined with a specific utility function the review s unambiguous conclusions about the need for extreme immediate action will not survive the substitution of assumptions that are consistent with today s marketplace real interest rates and savings rates