risk aversion and the recommended hedging ratio in a recent article in this journal kahl reviewed the existing literature on the determination of optimal futures and cash market positions the optimal hedging ratios were found to depend on whether the cash position was treated as endogenous or predetermined and some general implications were set forth the surprising conclusion was that the optimal hedging ratio is independent of the individual s risk aversion even though the optimal positions in the cash and futures markets are themselves not independent of the risk parameter kahl demonstrates that this conclusion

agricultural price instability a survey of competing explanations and remedies there are two explanations for agricultural price dynamics one follows cobweb logic and models fluctuations driven by expectation errors but emphasises that these expectations create complex dynamics and possibly chaos the other stems from the rational expectations tradition of dynamics driven by real shocks the empirical evidence tends to support the latter but is not conclusive the rational expectations model generates an optimal dynamic path from which no improvement can be expected from public intervention however if we take account of all the potential market failures in agricultural markets and especially in developing countries this conclusion might require some qualifications although an appropriate policy design for stability has still to be achieved this paper surveys the positive and normative literature on agricultural prices highlighting empirical evidence and identifying remaining unresolved issues

premia for correlated default risk abstract using data on corporate default experience in the u s and market rates of cdx index and tranche swaps of various maturities we estimate reduced form models of correlated default timing in the cdx high yield and investment grade portfolios under actual and risk neutral probabilities the striking contrast between the estimated processes followed by the actual and risk neutral arrival intensities of defaults and between the parameters governing the actual and risk neutral dynamics of the risk neutral intensities indicates the presence of substantial default risk premia in cdx swap market rates the effects of risk premia on swap rates covary strongly across maturities and depend on general stock market volatility and several measures of credit spreads large moves in the effects of these premia on swap rates have natural interpretations in terms of economic and financial market developments during the sample period april 2004 to october 2007 our results suggest that a large portion of the movements in cdx swap market rates observed during the sample period may be caused by changing attitudes toward correlated default risk rather than changes in the economic factors affecting the actual risk of clustered defaults which ultimately governs swap payoffs

price dispersion price flexibility and repeated purchasing this paper presents a search model in which consumers repeatedly purchase a commodity the repetition of purchases leads to the formation of implicit contracts with sellers which generate a kink in the demand curve facing each seller these kinks can generate equilibrium price dispersion under conditions where single purchase search models predict no price dispersion despite the kinks prices are at least partially flexible in that some and possibly all sellers change their prices in response to changes in production costs or demand dispersion de prix flexibilite des prix et achats repetes ce memoire presente un modele de recherche dans lequel les consommateurs font des achats repete s d un bien la repetition de l achat entraine la formation de contrats implicites avec les vendeurs ceci cree un pli dans la cedule de demande a laquelle chaque vendeur fait face ces plis peuvent engendrer une dispersion des prix d equilibre alors que le meme modele ne predirait aucune dispersion de prix en l absence d achats repet s malgre les plis les prix sont au moins partiellement flexibles puisque certains vendeurs tous peut re peuvent changer leurs prix en reponse a des changements dans les cofuts de production ou dans la demande

exploring the sources of default clustering abstract we study the sources of corporate default clustering in the united states we reject the hypothesis that firms default times are correlated only because their conditional default rates depend on observable and latent systematic factors by contrast we find strong evidence that contagion through which the default by one firm has a direct impact on the health of other firms is a significant clustering source the amount of clustering that cannot be explained by contagion and firms exposure to observable and latent systematic factors is insignificant our results have important implications for the pricing and management of correlated default risk

taxing fossil fuels under speculative storage long term environmental consequences of taxing fossil fuel usage have been extensively studied in the literature however these taxes may also impose several short run macroeconomic policy challenges the nature of which remains underexplored this paper investigates the mechanisms through which environmental taxes on fossil fuel usage can affect the main macroeconomic variables in the short run we concentrate on a particular mechanism speculative storage formulating and using a dynamic stochastic general equilibrium dsge model calibrated for the united states with an explicit storage facility and nominal rigidities we show that in designing environmental tax policies it is crucial to account for the fact that fossil fuel prices are subject to speculation the existence of forward looking speculators in the model improves the effectiveness of tax policies in reducing fossil fuel usage improved policy effectiveness however is costly it drives inflation and interest rates up while impeding output based on this tradeoff we seek an answer to the question how monetary policy should interact with environmental tax policies in our dsge model of fossil fuel storage we show that in an environment with no speculative storers monetary policy should respond to output along with cpi inflation in order to minimize the welfare losses brought by taxes however when the storage facility is activated responding to output in the monetary policy rule becomes less desirable

estimation of dynamic nonlinear rational expectations models of primary commodity markets with stochastic dynamic programming and disequilibrium maximum likelihood methods are combined to estimate a dynamic nonlinear rational expectations model of a market for a storable primary commodity the estimation model captures the inherently nonlinear structure of private stockholding dynamics the disequilibrium effects of government buffer stock intervention and the impact of price expectations and risk on private supply and stockholding decisions copyright 1993 by mit press

evaluating the economic cost of natural gas strategic storage restrictions the european commission wants to implement a single market for gas one of the components of this market is a regulated provision for security of supply which consists of rules for the implementation and use of a given reserve stock of gas we investigate the impact of this policy on the profitability of a storage operator using data from denmark and italy keeping storage capacity constant the costs of the strategic stock are around 20 of the value of the storage market for denmark and 16 for italy this cost is due to the inability to extract arbitrage profits from the captive stock furthermore the strategic storage restriction induces behavior that would virtually never be replicated by a private storage operator in an unconstrained market in particular in the first 6 months of the year when unconstrained firms empty their reservoirs much faster suggesting the strategic restriction is unnecessarily distorting the market c 2010 published by elsevier b v less

dynamic programming models and algorithms for the mutual fund cash balance problem fund managers have to decide the amount of a fund s assets that should be kept in cash considering the trade off between being able to meet shareholder redemptions and minimizing the opportunity cost from lost investment opportunities in addition they have to consider redemptions by individuals as well as institutional investors the current performance of the stock market and interest rates and the pattern of investments and redemptions that are correlated with market performance we formulate the problem as a dynamic program but this encounters the classic curse of dimensionality to overcome this problem we propose a provably convergent approximate dynamic programming algorithm we also adapt the algorithm to an online environment requiring no knowledge of the probability distributions for rates of return and interest rates we use actual data for market performance and interest rates and demonstrate the quality of the solution compared to the optimal for the top 10 mutual funds in each of nine fund categories we show that our results closely match the optimal solution in considerably less time and outperform two static newsvendor models the result is a simple policy that describes when money should be moved into and out of cash based on market performance

speculative intensity and spot and futures price variability this paper develops a simultaneous stochastic rational expectations model of futures and spot price determination using the model we find that increases in what we term speculative intensity increase spot price variability arising from storage cost shocks but decrease spot price variability arising from demand shocks in contrast increases in speculative intensity unambiguously decrease futures price variability regardless of the underlying source of disturbances we are able to develop these comparative static results because the model has a unique equilibrium

price stabilization using buffer stocks abstract the price stabilization problem is stated and solved for a nonlinear cobweb model with government stocks it is shown that if the storage capacity for the commodity is sufficiently large then there exists a simple stabilization policy called the keep supply at equilibrium kse policy such that the equilibrium price is a global attractor for the corresponding closed loop system in addition it is shown that if the government approximates the equilibrium supply with the average supply stabilization is guaranteed we refer to this policy as keep supply at average ksa

price dispersion in an automobile insurance market from automobile insurance data for alberta over the period 1974 81 we find thatpremiums are highly correlated across driver classes in a given year but that premiums for a given driver class are not correlated over a period of more than 5 years firms relative market shares among drivers over age 25 and married males under 25 are inversely related to their deviations from the mean premiums in these driver classes the variance of real premiums decreases with the numberof firms in the market and increases with the real loss cost per car insured and the number of cars insured from these results we conclude that the price dispersion in automobile insurance in alberta is based on costly consumer search

the empirical merit of structural explanations of commodity price volatility review and perspectives this paper presents both the history of and state of the art in empirical modeling approaches to the world commodity price volatility the analysis builds on the storage model and key milestones in its development specifically it is intended to offer a reader unfamiliar with the relevant literature an insight into the modeling issues at stake from both a historical and speculative viewpoint the review considers primarily the empirical techniques designed to assess the merits of the storage theory it does not address purely statistical approaches that do not rely on storage theory and that have been studied in depth in other streams of the commodity price literature the paper concludes with some suggestions for future research to try to resolve some of the existing empirical flaws and hopefully to increase the explanatory power of the storage model

food security and storage in the middle east and north africa in times of highly volatile commodity markets governments often try to protect their populations from rapidly rising food prices which can be particularly harsh for the poor a potential solution for food deficit countries is to hold strategic reserves which can be called on when international prices spike but how large should strategic stockpiles be this paper develops a dynamic storage model for wheat in the middle east and north africa mena region where imported wheat dominates the average diet the paper uses the model to analyze a strategy that sets aside wheat stockpiles which can be used when needed to keep domestic prices below a targeted price this paper shows that if the target is set high and reserves are adequate the strategy can be effective and robust contrary to most interventions strategic storage policies are counter cyclical and when the importing region is sufficiently large a regional policy can smooth global prices this paper shows that this is the case for the mena region nevertheless the policy is more costly than the pro cyclical policy of a targeted intervention that directly offsets high prices with a subsidy similar to food stamps

fast pricing of basket default swaps a basket default swap is a derivative security tied to an underlying basket of corporate bonds or other assets subject to credit risk the value of the contract depends on the joint distribution of the default times of the underlying assets valuing a basket default swap often entails monte carlo simulation of these default times for baskets of high quality credits and for swaps that require multiple defaults to trigger payment pricing the swap is a rare event simulation problem the joshi kainth algorithm is an innovative importance sampling technique for this problem that forces a predetermined number of defaults to occur on each path this paper analyzes extends and improves the joshi kainth algorithm we show that in its original form the algorithm can actually increase variance we present an alternative that is guaranteed to reduce variance even when defaults are not rare along the way we provide a rigorous underpinning in a setting sufficiently general to include both the original method and the version proposed here

food security policy in a stochastic world abstract food security may be increased by variance reducing strategies by food aid or by development strategies this paper uses a korea cge model subjected to random fluctuation in world prices and domestic food productivity to evaluate these policies we find that poverty reducing development strategies are the most food security strategies

a top down approach to multiname credit a multiname credit derivative is a security that is tied to an underlying portfolio of corporate bonds and has payoffs that depend on the loss due to default in the portfolio the value of a multiname derivative depends on the distribution of portfolio loss at multiple horizons intensity based models of the loss point process that are specified without reference to the portfolio constituents determine this distribution in terms of few economically meaningful parameters and lead to computationally tractable derivatives valuation problems however these models are silent about the portfolio constituent risks they cannot be used to address applications that are based on the relationship between portfolio and component risks for example constituent risk hedging this paper develops a method that extends these models to the constituents we use random thinning to decompose the portfolio intensity into a sum of constituent intensities we show that a thinning process which allocates the portfolio intensity to constituents uniquely exists and is a probabilistic model for the next to default we derive a formula for the constituent default probability in terms of the thinning process and the portfolio intensity and develop a semi analytical transform approach to evaluate it the formula leads to a calibration scheme for the thinning processes and an estimation scheme for constituent hedge sensitivities an empirical analysis for september 2008 shows that the constituent hedges generated by our method outperform the hedges prescribed by the gaussian copula model which is widely used in practice

time changed birth processes and multiname credit derivatives a credit investor such as a bank granting loans to firms or an asset manager buying corporate bonds is exposed to correlated corporate default risk a multiname credit derivative is a financial security that allows the investor to transfer this risk to the credit market in this paper we study the valuation and risk analysis of multiname derivatives to capture the complex economic phenomena that drive the pricing of these securities we introduce a time changed birth process as a probabilistic model of correlated event timing the self exciting property of a time changed birth process captures the feedback from events that is often observed in credit markets the stochastic variation of arrival rates between events captures the exposure of firms to common economic risk factors we derive a closed form expression for the distribution of a time changed birth process and develop analytically tractable pricing relations for a range of multiname derivatives valuation problems we illustrate our results by calibrating a tranche forward and option pricer to market rates of index and tranche swaps

product quality and imperfect information this paper considers markets in which consumers are imperfectly informed about both product prices and quality levels offered by firms we characterize necessary and sufficient conditions for existence of the various equilibrium configurations of price and quality that can arise in two paradigm cases when all consumers prefer higher quality and when all consumers prefer lower quality our results suggest that firms will exploit imperfect information by charging noncompetitive prices as well as by offering other than ideal quality in the former case but only by changing noncompetitive prices in the latter case

physician market power evidence from the allocation of malpractice premiums norman k thurston based on evidence from variations in malpractice premiums physicians have local market power at least in some dimensions it is observed that higher cost physicians pass on a significant portion of idiosyncratic costs to patients as higher prices i test two hypothesized sources of this market power barriers to entry from specialization and relatively inelastic firm level demand for certain services examining the relationship of physician specific malpractice premiums to fees i find no observable difference in the ability of surgeons and nonsurgeons to pass on these costs however both types of physicians pass them on more to surgical than to nonsurgical patients jel l11 i11 i introduction two of the most interesting unanswered questions with regard to markets for physician services are whether physicians enjoy market power that affects their price setting behaviors and if so what the source of such market power might be one frequent hypothesis is that asymmetric information regarding quality gives physicians market power that varies depending on the type of services sought by patients markets for common services office visits are thought to be more competitive than less frequently sought services surgeries another possibility is that supply restrictions in medical education coupled with the specialization and certification process creates barriers to entry giving specialists a greater degree of market power than generalists i perform tests of these hypotheses by looking at how physicians allocate fixed costs to prices economic theory suggests that the ability to pass on higher than average fixed costs to customers in the form of higher prices is directly related to the existence of local market power for physicians malpractice premiums provide a unique opportunity to examine this problem i utilize individual specific variation in malpractice premiums to test whether this market power is observable due to either specialization or patient type i find empirical evidence of market power based on patient heterogeneity but not based on specialization malpractice insurance premiums represent a substantial portion of physicians costs 1 malpractice insurance protects doctors from liability settlements arising out of patients claims that they failed to follow acceptable procedures tort law requires physicians to use skills commensurate with their class of practitioner u s house of representatives 1990 89 because collected premiums must cover insurers costs rising malpractice premiums are simply reflections of the rising costs of providing this service premiums are set by the insurer subject to approval by state insurance regulatory agencies a base fee is set for the physician s geographical location usually the state then adjustments are made to account for specific geographic areas such as major metropolitan areas versus rural areas 2 the riskiness of the type of practice is also assessed specialty classes are assigned multipliers yielding the approximate annual premium which is fairly constant within markets and specialty classes one of the most striking features of the structure of malpractice premiums is that after controlling for important factors that determine base premiums for physician risk categories there is still substantial variation in premiums paid the choice of coverage that a policy will carry the maximum amounts payable for one case and total payment is an important consideration other adjustments are made if a physician performs high risk procedures or if the insurer has responded to claims against the physician in the past u s house of representatives 1990 31 41 however formal experience rating is not common given the nature of the institutions a small set of information describing a practice s structure history and location is sufficient to separate the malpractice premium into the common base fee and the individual specific component

a generalized model of pricing for homogeneous goods under imperfect information this paper generalizes the model developed in wilde and schwartz 1979 to allow downward sloping demand curves and u shaped average cost curves it shows that the basic qualitative conclusions of wilde and schwartz still hold moreover it shows that the critical proportion of comparison shoppers needed to generate a competitive equilibrium falls as demand becomes more elastic or average costs become more inelastic finally it shows that when imperfect information generates non competitive outcomes they are bounded below in welfare terms by the monopolistically competitive equilibrium

a quantile autoregression analysis of price volatility in agricultural markets this paper investigates the dynamics of agricultural price volatility based on a quantile autoregression qar model the qar model provides a flexible representation of the distribution of price and its dynamics the approach is applied to u s wheat and corn markets over the period of 1980 2017 this period is of significant interest as it covers important changes in agricultural policy and increased reliance on markets the price analysis is conducted conditional on stocks held in the previous period we show how increasing previous stocks shift the price distribution to the left and decreases the odds of facing price spikes by shifting down the upper tail of the price distribution our analysis also examines the effects of changing public stocks on prices for both wheat and corn this reflects changing agricultural policy contrasting the 1980s when public stocks were relatively high with the post 2005 period when public stocks became zero we document how higher public stock ratio during the previous period did not lower the odds of facing price spikes applied to the wheat and corn markets we also uncover evidence of local dynamic instability in the upper tail of the price distribution suggesting that price instability becomes more pronounced when previous stocks are low

the economic role of commodity storage one of the earliest and most successful exainples of economic policy is the oftquoted biblical account of joseph s interpretation of the pharoah s dream joseph foretold that seven years of abundant harvests would precede seven years of drought and recommended that the pharoah accumulate grain during the good years since that time the central role of storage in stabilising the economy in the face of exogenous disturbances has been obvious but our understanding of the nature of that role has not greatly advanced without divine assistance in forecasting stochastic production the storage decision is considerably more complex than the one joseph faced and the role of storage quite different in fact several commonly held impressions about the role of storage of commodities such as grains are incorrect rather than stabilising production storage actually accentuates its variability rather than causing a mean price preserving decrease or a mean output preserving decrease in the dispersion of price storage generally causes a more complex modification of the distribution of price rather than being most effective at eliminating short falls in consumption storage actually is more effective at eliminating the incidence of exceedingly high consumption in this paper we explore the role of storage in a model where production is stochastic and both production and storage are performed by competitive profitmaximisers who form rational expectations about the returns to their activities we derive the subtle but very important interactions among production price expectations and storage which simpler models cannot capture finally we make a comparative statics assessment of the distributional implications of storage these results while confirming the importance of the specification of the demand function and the supply elasticity identified in recent analytical studies e g wright i979 and newbery and stiglitz i979 are surprisingly favourable to consumers considering the asymmetric nature of the effects of storage on consumption and price storage is simply a productive activity one that transfers a commodity from one period to the next like other forms of production it is costly the total cost of storing an amount st from period t to period t i is as of period t i

inflation targeting learning and q volatility in small open economies this paper examines the welfare implications of managing asset price with consumer price inflation targeting by monetary authorities who have to learn the laws of motion for both inflation rates the central bank can reduce the volatility of consumption as well as improve welfare more effectively if it adopts state contingent taylor rules aimed at inflation and q growth targets in this learning environment however under perfect model certainty pure inflation targeting dominates combined consumer and asset price inflation targeting

common failings how corporate defaults are correlated we test the doubly stochastic assumption under which firms default times are correlated only as implied by the correlation of factors determining their default intensities using data on u s corporations from 1979 to 2004 this assumption is violated in the presence of contagion or frailty unobservable explanatory variables that are correlated across firms our tests do not depend on the time series properties of default intensities the data do not support the joint hypothesis of well specified default intensities and the doubly stochastic assumption we find some evidence of default clustering exceeding that implied by the doubly stochastic model with the given intensities why do corporate defaults cluster in time several explanations have been explored first firms may be exposed to common or correlated risk factors whose co movements cause correlated changes in conditional default probabilities second the event of default by one firm may be contagious in that one such event may directly induce other corporate failures as with the collapse of penn central railway in 1970 third learning from default may generate default correlation for example to the extent that the defaults of enron and worldcom revealed accounting irregularities that could be present in other firms they may have had a direct impact on the conditional default probabilities of other firms our primary objective is to examine whether cross firm default correlation that is associated with observable factors determining conditional default probabilities the first channel on its own is sufficient to account for the degree of time clustering in defaults that we find in the data

is regulation necessary for value of service pricing this article presents evidence for the existence of value of service pricing in the neverregulated market for trucking services to haul florida produce rates per truckload are found to increase by eleven to twelve cents for every one dollar increase in the average daily loss in the value of the cargo due to product deterioration ceteris paribus this result is at variance with the commonly held belief that value of service pricing in transportation is a form of price discrimination made possible by the policies of rate bureaus and regulatory agencies

endogenous diffusion of technology abstract this paper presents a positive theory of diffusion of technology it examines a two period model strategic firms are confronted by a process technology with an uncertain reduction in marginal costs the uncertainty is automatically resolved between the two periods adoption in the first period yields a leadership advantage relative to firms that do not adopt while simultaneous adoption by firms results in a cournot equilibrium the firms strategies are both production quantities and adoption timings these decisions are made at the same time thus firms face a trade off between early adoption and possibly reaping first mover advantages on one hand and deferring the adoption decision until after all the uncertainty is resolved but face the possibiity of being a follower in the market interestingly an endogenously determined diffusion rate is obtained as a pure strategy nash equilibrium of this game this means that while adoption and diffusion of technology results with probability one diffusion of a bad innovation is also possible it is also shown that in a market with one large firm and a nonatomic continuum of small firms there is a unique nash equilibrium in which the large firm adopts first and is a stackelberg leader and all the small firms decide whether or not to adopt after the uncertainty is resolved the implication of this result is simply that the diffusion of technology is to some extent determined by the relative size of firms in the industry

risk analysis of collateralized debt obligations collateralized debt obligations which are securities with payoffs that are tied to the cash flows in a portfolio of defaultable assets such as corporate bonds play a significant role in the financial crisis that has spread throughout the world insufficient capital provisioning due to flawed and overly optimistic risk assessments is at the center of the problem this paper develops stochastic methods to measure the risk of positions in collateralized debt obligations and related instruments tied to an underlying portfolio of defaultable assets it proposes an adaptive point process model of portfolio default timing a maximum likelihood method for estimating point process models that is based on an acceptance rejection resampling scheme and statistical tests for model validation to illustrate these tools they are used to estimate the distribution of the profit or loss generated by positions in multiple tranches of a collateralized debt obligation that references the cdx high yield portfolio and the risk capital required to support these positions

the behavior of commodity prices in ethiopia in an attempt to identify price stabilization strategies and rationalize public intervention in buffering markets this article investigates the intertemporal dynamics of commodity prices in ethiopia a classical rational expectation model is modified to account for seasonal correlation of shocks model predictions are reduced to computable periodic threshold autoregression several nonlinearity tests are applied to detect threshold effects a regime switching normalized maximum likelihood method is formulated to estimate thresholds and threshold autoregression parameters using monthly data from ethiopia for the period 1996 2006 the result indicates the presence of periodic price thresholds that could be formed as a result of speculative storage comparison of price movements below and above thresholds indicates that prices are more correlated below the thresholds than above them however the effect on error variance is not very strong temporal arbitrage which is the gross return from speculative storage appears to be modest the long and short term implications of the findings are discussed within the context of ongoing policy debates

a two season agricultural household model of output and price uncertainty abstract this paper presents a two season model of a household s production consumption labor supply and storage decisions in an environment of output and price risk the analytical results in this study are markedly different from those of models prevalent in the mainstream of the agricultural household literature the empirical analysis that uses panel data from a village in india provides support for the theoretical results and underscores the seasonal dimension of the farmers choice problems the results also show that ignoring risk or risk averse preferences may introduce substantial downward bias in optimal response estimates

the risk of a mortality catastrophe we develop a continuous time model for analyzing and valuing catastrophe mortality contingent claims based on stochastic modeling of the force of mortality we derive parameter estimates from a 105 year time series of u s population mortality data using a simulated maximum likelihood approach based on a particle filter relying on the resulting parameters we calculate loss profiles for a representative catastrophe mortality transaction and compare them to the official loss profiles that are provided by the issuers to investors and rating agencies we find that although the loss profiles are subject to great uncertainties the official figures fall significantly below the corresponding risk statistics based on our model in particular we find that the annualized incidence probability of a mortality catastrophe defined as a 15 increase in aggregated mortality probabilities is about 1 4 compared to about 0 1 according to the official loss profiles

the prebisch singer hypothesis a reappraisal independent of stationarity hypotheses time series behaviour of the relative price of primary commodities raul prebisch i950 and hans singer i950 believed that the long term trend of primary commodity prices was negative the latter in an interesting discussion of the above quandary pp 482 3 viewed rises in primary commodity prices as purely temporary sources of surplus that offered short lived opportunities to increase industrial investment these opportunities were missed by private investors who instead increased primary sector investment in such circumstances because all private activity tends to be governed by the price