are biofuels a feasible option abstract recently a number of objections have been raised against the use of ethanol produced from agricultural products such as maize sugarcane wheat or sugar beets as a replacement for gasoline despite some of their advantages such as being cleaner and to some extent renewable we address these objections in this paper topics discussed include the corn connection which was theorized to be a cause of deforestation in the amazonia the rise of food prices due to ethanol production and the real possibilities of ethanol in reducing greenhouse gas emissions it has been shown that such concerns are grossly exaggerated and that ethanol from sugarcane as produced in brazil is the preferred option for the production of fuel not only in terms of cost but also as a favourable energy balance finally the possibility of expanding ethanol production to other sugar producing countries is also discussed

manipulations by coalitions under asymmetric information the case of groves mechanisms abstract we study the formation in coalitions in vickrey clarke groves mechanisms in a model where we assume that asymmetry of information exists within coalitions the coalitions must therefore use an internal mechanism to give incentives to their members to reveal their information to each other we show that there exists no mechanism robust to all coalitions on the other hand there exist mechanisms robust to coalitions of two agents and any larger coalition that would form in these mechanisms would be subject to manipulation by subcoalitions we characterize these mechanisms and show in particular that they are never anonymous journal of economic literature classification numbers c71 d82

group incentive compatibility in a market with indivisible goods abstract in a market where each trader has one unit of an indivisible good there are procedures for exchanging goods which result in competitive allocations one of these procedures the top trading cycle has the property that it is in each trader s best interest to report his true preferences over the set of goods this note shows that no subset of traders can misrepresent their preferences and improve the allocation for all members of the subset additionally if there are no indifferences in the preferences then some traders in a subset that misrepresents preferences do worse

biofuels what a biopact between north and south could achieve abstract with very few exceptions such as the recent remarks by international energy agency iea head claude mandil commentators on the world s energy issues have yet to recognize the enormous contribution that biofuels producers from the south could make to solving the world s greenhouse gas emission problems and problems to do with the peaking of oil supplies once the equation between biofuels and high cost land intensive cultivation in the north is broken and a quite different scenario involving production in the south is adopted then the possibilities are dramatically changed the argument of this paper is that a transition to substitution of 20 percent of oecd gasoline needs by 2020 could be met from the south by creating the equivalent of 18 brazils over the course of the next decade such an enormous transition will not occur by itself or through the operation of market forces alone it needs an institutional framework one that guarantees for the countries of the north regular supplies of biofuels produced in a responsible manner and guarantees for the countries of the south open markets for the biofuels produced the oecd is in the best position to bring about such an arrangement through taking the initiative of offering developing countries a biopact between north and south thereby creating for the first time a global market for biofuels the launch of an international biofuels forum under the auspices of the un in early 2007 is a step towards the creation of such an international framework where north south issues on biofuels may be fruitfully addressed

efficient resource allocation on the basis of priorities many institutions allocate resources by non market mechanisms based on priorities in this paper we introduce a model of resource allocation on the basis of priorities and address the following questions is it possible to allocate resources on the basis of any priority structure if yes when can we do this pareto efficiently without creating incentives for manipulation and consistently across different groups of agents and resource levels we adopt a basic indivisible objects model with a finite number of object types and a finite quota of goods of each type some interesting examples are the determination of access to education allocation of graduate houses offices or tasks agents are assumed to have strict preferences over object types and remaining unassigned an assignment is an allocation of the objects to the agents such that every agent receives at most one object a rule associates an assignment to each preference profile we formalize a priority structure to be a collection of strict priority rankings of individuals indexed by the object types where i a j would be read as i has higher priority for object a than j we assume that the priority structure is exogenously fixed and allow the preferences of the agents to vary a rule is said to violate a priority of i for a if there is a preference profile under which i envies j who is assigned a and publication information econometrica 70 6 november 2002 2489 2497 the copyright to this article is held by the econometric society http www econometricsociety org it may be downloaded printed and reproduced only for personal or classroom use absolutely no downloading or copying may be done for or on behalf of any for profit commercial firm or other commercial purpose without the explicit permission of the econometric society for this purpose contact julie p gordon executive director of the society at jpg northwestern edu i would like to thank faruk gul wolfgang pesendorfer the co editor the four anonymous referees and the participants of the micro theory lunch seminar in princeton university for their comments and suggestions

on two competing mechanisms for priority based allocation problems we consider the priority based allocation problem there is a set of indivisible objects with multiple supplies e g schools with seats and a set of agents e g students with priorities over objects e g proximity of residence area we study two well known and competing mechanisms the agentoptimal stable mechanism aosm allots objects via the deferred acceptance algorithm the top trading cycles mechanism ttcm allots objects via gale s top trading cycles algorithm we show that the two mechanisms are equivalent or ttcm is fair i e respects agents priorities or resource monotonic o rpopulation monotonic if and only if the priority structure is acyclic furthermore if aosm fails to be efficient consistent for a problem ttcm also fails to be fair consistent for it however the converse is not necessarily true

stable and efficient resource allocation under weak priorities abstract we study the indivisible object allocation problem without monetary transfer in which each object is endowed with a weak priority ordering over agents it is well known that stability is generally not compatible with efficiency we characterize the priority structures for which a stable and efficient assignment always exists as well as the priority structures that admit a stable efficient and group strategy proof rule while house allocation problems and housing markets are two classic families of allocation problems that admit a stable efficient and group strategy proof rule any priority augmented allocation problem with more than three objects admits such a rule if and only if it is decomposable into a sequence of subproblems each of which has the structure of a house allocation problem or a housing market

the pricing of options on assets with stochastic volatilities one option pricing problem that has hitherto been unsolved is the pricing of a european call on an asset that has a stochastic volatility this paper examines this problem the option price is determined in series form for the case in which the stochastic volatility is independent of the stock price numerical solutions are also produced for the case in which the volatility is correlated with the stock price it is found that the black scholes price frequently overprices options and that the degree of overpricing increases with the time to maturity one option pricing problem that has hitherto remained unsolved is the pricing of a european call on a stock that has a stochastic volatility from the work of merton 12 garman 6 and cox ingersoll and ross 3 the differential equation that the option must satisfy is known the solution of this differential equation is independent of risk preferences if a the volatility is a traded asset or b the volatility is uncorrelated with aggregate consumption if either of these conditions holds the risk neutral valuation arguments of cox and ross 4 can be used in a straightfoward way this paper produces a solution in series form for the situation in which the stock price is instantaneously uncorrelated with the volatility we do not assume that the volatility is a traded asset also a constant correlation between the instantaneous rate of change of the volatility and the rate of change of aggregate consumption can be accommodated the option price is lower than the blackscholes b s 1 price when the option is close to being at the money and higher when it is deep in or deep out of the money the exercise prices for which overpricing by b s takes place are within about ten percent of the security price this is the range of exercise prices over which most option trading takes place so we may in general expect the b s price to overprice options this effect is exaggerated as the time to maturity increases one of the most surprising implications of this is that if the b s equation is used to determine the implied volatility of a near the money option the longer the time to maturity the lower the implied volatility numerical solutions for the case in which the volatility is correlated with the stock price are also examined the stochastic volatility problem has been examined by merton 13 geske 7 johnson 10 johnson and shanno 11 eisenberg 5 wiggins 16 and

strategy proof exchange we consider the allocation of goods in exchange economies with a finite number of agents who may have private information about their preferences in such a setting standard allocation rules such as walrasian equilibria or rational expectations equilibria are not compatible with individual incentives we characterize the set of allocation rules which are incentive compatible or in other words the set of strategy proof social choice functions social choice functions which are strategy proof are those which can be obtained from trading according to a finite number of pre specified proportions the number of proportions which can be accommodated is proportional to the number of agents such rules are necessarily inefficient even in the limit as the economy grows

option prices and the underlying asset s return distribution this work examines the relation between option prices and the true as opposed to risk neutral distribution of the underlying asset if the underlying asset follows a diffusion with an instantaneous expected return at least as large as the instantaneous risk free rate observed option prices can be used to place bounds on the moments of the true distribution an illustration of the paper s results is provided by the analysis of the information concerning the mean and standard deviation of market returns contained in the prices of s p 100 index options although it seems natural that the prices of claims to various parts of the underlying asset s distribution should contain information about the shape of that distribution cox and ross 1976 established that an option s price equals its expected payoff discounted at the risk free rate where the expectation is taken over the risk neutral rather than the true distribution of the underlying asset linking the risk neutral distribution implicit in option prices to the true distribution remains a comparative mystery a necessary condition for the risk neutral pricing methodology to be applicable is that the true and the risk neutral distribution share a common support the only information about the true distribution that can be obtained from observed option prices alone is information about that support this paper demonstrates though that observed option prices when used in conjunction with simple assume d restrictions on the true distribution do contain information about the noncentral moments of the true distribution not directly implied by those assumed restrictions alone the intuition for the result that option prices can be useful in placing bounds on the moments of the true distribution is straightforward first we generalize the results in lo 1987 to show how the expected payoff to a call can be bounded above in terms of any chosen set of the noncentral moments of the return on the underlying asset second we establish restrictions on the

recovering probability distributions from option prices this article derives underlying asset risk neutral probability distributions of european options on the s p 500 index nonparametric methods are used to choose probabilities that minimize an objective function subject to requiring that the probabilities are consistent with observed option and underlying asset prices alternative optimization specifications produce approximately the same implied distributions a new and fast optimization technique for estimating probability distributions based on maximizing the smoothness of the resulting distribution is proposed since the crash the risk neutral probability of a three four standard deviation decline in the index about 36 percent 46 percent over a year is about 10 100 times more likely than under the assumption of lognormality recently the increasing popularity of derivatives and some highly publicized failures to control risk have led to increased efforts to find reasonable methods to measure the sensitivity of large institutional derivatives portfolios to extreme events merely because such events are rare is not sufficient to ignore them since on the few occasions when they do occur significant amounts of money can change hands potentially wiping out profits accumulated over long prior periods a key assumption behind methods of estimation is the joint probability distribution of constituent underlying asset returns this has long been a concern of financial economists since probability assumptions are critical to much of their research during the last quarter century heretofore probability distributions of stock market returns have typically been estimated from historical time series unfortunately common hypotheses may not capture the probability of extreme events and the events of interest are rare or may not be present in the historical record even though they are clearly possible

target zones and exchange rates an empirical investigation this paper develops an empirical model of exchange rates in a target zone the distribution of exchange rate changes is conditioned on a latent jump variable where the probability and size of a jump vary over time as a function of financial and macroeconomic variables when there is no jump the target zone is credible and exchange rate changes are constrained to remain within the target zone band the paper revisits the empirical evidence from the european monetary system regarding the conditional distribution of exchange rate changes the credibility of the system and the size of the foreign exchange risk premia in contrast to some previous findings we conclude that the french franc deutschmark rate exhibits considerable nonlinearities realignments are somewhat predictable and the credibility of the system did not increase substantially after 1987 moreover our model implies that the foreign exchange risk premium becomes large during speculative crises

collusion in second price auctions with heterogeneous bidders abstract we show that efficient collusion by any subset of bidders in second price private value auctions is possible even when the bidders are heterogeneous an important property of efficient collusion is that a bidder s net payoff from participating in collusion is independent of her valuation we show that the cooperative game whose characteristic function evaluated at a coalition is the ex ante collusive surplus of that coalition has a nonempty core a feature of more technical interest is the mechanism characterization when the private information of agents does not enter in a linear or even piecewise linear manner

efficient resource allocation under multi unit demand abstract we study resource allocation with multi unit demand such as the allocation of courses to students in contrast to the case of single unit demand no stable mechanism not even the student proposing deferred acceptance algorithm achieves desirable properties it is not strategy proof and the resulting allocation is not even weakly efficient under submitted preferences we characterize the priority structure of courses over students under which stability is consistent with strategy proofness or efficiency we show that stability is compatible with strategy proofness or efficiency if and only if the priority structure is essentially homogeneous this result suggests that efficient allocation under multi unit demand is difficult and that the use of stable mechanisms may not deliver desirable outcomes

ethanol production food and forests this paper investigates the direct and indirect impacts of ethanol production on land use deforestation and food production a partial equilibrium model of a national economy with two sectors and two regions one of which includes a forest is developed it analyses how an exogenous increase in the ethanol price affects input allocation land and labor between sectors energy crop and food the total effect of ethanol prices on food production and deforestation is decomposed into three partial effects first the well documented effect of direct land competition between rival uses arises it increases deforestation and decreases food production second an indirect displacement of food production across regions possibly provoked by the reaction of international food prices increases deforestation and reduces the food sector s output finally labor mobility between sectors and regions tends to decrease food production but also deforestation the total impact of ethanol production on food production is negative while there is an ambiguous impact on deforestation

collusive bidder behavior at single object second price and english auctions models of collusive bidder behavior at single object second price and english auctions are provided the ind ependent private values model is generalized to permit the formulatio n of coalitions and a strategic response by the auctioneer cooperati ve strategies are found to be dominant in these models coalitions of any size are viable and the payoff to each member increases with th e size of the coalition in addition the collusive strategies of the coalition represent a noncooperative equilibrium the optimal respon se of the auctioneer is to establish a reserve price that is a functi on of the coalition s size these and other features of the model are found to be consistent with the essential features of actual behavio r copyright 1987 by university of chicago press

using option prices to estimate realignment probabilities in the european monetary system the case of sterling mark abstract this paper describes a procedure for estimating the market s perceived probability distribution of future exchange rates from the prices of risk reversals strangles and other currency options and uses the procedure to estimate the risk neutral ex ante probability of a realignment of the pound sterling the procedure for estimating the realignment probabilities relies on the jump diffusion model of exchange rate behavior and the resulting option pricing formula by fitting this model to market option price data i retrieve the unobserved parameters of the jump diffusion process i then use these parameter estimates to estimate the ex ante probability distribution of exchange rates and thus the realignment probabilities

manipulation and single peakedness a general result this article considers environments in which individual preferences are single peaked with respect to an unspecified but unidimensional ordering of the alternative space we show that in these environments any institution that is coalitionally strategy proof must be dictatorial thus any nondictatorial institutional environment that does not explicitly utilize an a priori ordering over alternatives in order torendera collectivedecisionis necessarilyprone to the strategic misrepresentation of preferences by an individual or a group moreover we prove in this environment that for any nondictatorial institution the truthful revelation of preferences can never be a dominant strategy equilibrium accordingly an incentive to behave insincerely is inherent to the vast majority of real world lawmaking systems even when the policy space is unidimensional and the core is nonempty t hequestionofmanipulation themisrepresentation of one s true preferences in order to achieve a more favorable collective decision has alternately intrigued and frustrated social scientists for over two centuries 1 manipulation is clearly a potential problem for those interested in drawing inferences from individuals observed behaviors for example how does a legislator s roll call vote relate to his or her policy preferences how does an individual voter s vote choice reflect his or her preferences over the parties and or candidates moresubtly doesthecompositionofalegislativecommittee reflect the preferences of the members of the legislature does a juror s vote to convict a defendant truthfully reflect the juror s beliefs about the defendant s guilt or innocence is the president s choice of political appointees indicative of the policies that he or she would pursue in their positions in short manipulation is simultaneously

arbitrage based tests of target zone credibility evidence from erm cross rate options this paper introduces two arbitrage based tests of target zone credibility using a new data source exchange rate mechanism cross rate options using daily option prices from september 1991 to august 1994 the authors assess the credibility of the pound mark and mark lira target zones that collapsed in september 1992 and the ongoing mark french franc target zone these tests are based on restrictions that must apply to all option prices within a credible target zone and are free from specification error and estimation error the authors also identify a minimum intensity of realignment an expression indicating the probability weighted average realignment size copyright 1996 by american economic association

an interpretation of recent research on exchange rate target zones how do exchange rate bands work compared to completely fixed rates between realignments or more precisely what are the dynamics of exchange rates interest rates and central bank interventions within exchange rate bands does the difference between bands and completely fixed exchange rates matter and if so which of the two arrangements is best or more precisely what are the tradeoffs that determine the optimal bandwidth this article will present an interpretation of some selected recent theoretical and empirical research on exchange rate target zones with emphasis on main ideas and results and without technical detail

economic and policy issues in the production of algae based biofuels a review despite the initial environmental and supply benefits associated with conventional biofuels leading to substantial policy support research has indicated that these benefits might have been overly optimistic negative externalities associated with food and resource allocation have also resulted in an increasing scepticism about the long term potential of transitioning to biofuels this review presents the economic benefits and costs surrounding conventional biofuels and suggests the need for further development of a third generation feedstock based on algae the article provides guidance on the potential for a policy framework for supporting microalgae as a source of biofuels given the numerous associated positive externalities

the alcohol program the rational for the launching of the alcohol program from sugarcane in brazil in the mid 1970 s is described as an answer to the first oil crisis as well as a solution to the problem of the fluctuating sugar prices in the international market the technical characteristics of ethanol as a fuel are given as well as a discussion of the evolution of the cost of production environmental and social consequences regarding costs ethanol production was close to 100 dollars a barrel in the initial stages of the program in 1980 falling rapidly due to economies of scale and technological progress to half that value in 1990 followed by a slower decline in recent years considering the hard currency saved by avoiding oil importation through the significant displacement of gasoline by ethanol and the decrease in the amount of external debt that the displaced oil importation was able to provide it is possible to demonstrate that the alcohol program has been an efficient way of exchanging dollar debt by national currency subsidies which are paid by the liquid fossil fuel users even with this economic gains for society the continuity of the program is difficult to maintain two solutions to this problem are discussed internal expansion of the use of ethanol and exports to industrialized countries where it could be used as an octane enhancer the main attractiveness of the program the reduction of co2 emissions as compared to fossil fuels is stressed mainly as a solution for industrialized countries to fulfill their commitments with the united nations framework climate change convention

house allocation with transfers we consider the shapley scarf house allocation problem where monetary transfers are allowed we characterize the class of mechanisms that are strategy proof ex post individually rational ex post budget balanced and collusion proof in these mechanisms the price of each object is fixed in advance and the objects are reallocated according to the unique core assignment of the shapley scarf economy associated with the prices the special case in which all prices are zero is the core mechanism studied by shapley and scarf our mechanisms are compelling alternatives to the groves mechanisms which satisfy neither budget balance nor our condition of collusion proofness journal of economic literature classification numbers c71 c78 d71 d78 d89

house allocation with existing tenants an equivalence abstract we analyze two mechanisms designed to eliminate inefficiencies in house allocation problems where there are both existing tenants and newcomers the first mechanism chooses the unique core allocation of a sister exchange economy constructed by endowing each existing tenant with her current house and each newcomer with a random vacant house the second mechanism chooses an ordering from a given distribution and determines the final outcome as follows assign the agents the best available house one at a time following their ordering in the queue and whenever an agent demands the house of an existing tenant who is still in the line modify the queue by inserting the existing tenant at the top whenever a loop of existing tenants forms assign each of them the house she demands and proceed we show that the first mechanism is equivalent to an extreme case of the second which favors the newcomers

how biofuel policies backfire misguided goals inefficient mechanisms and political ecological blind spots abstract the development of an economically viable biofuel industry rests on strong state subsidies for production and processing creation of markets through government procurement fuel blending mandates price controls as well as foreign trade tariffs and quotas and multiple interventions in agricultural ecological and other regulations we use an approach grounded in agrarian political economy to critically analyze the literature on how biofuel policies interact with broader production trade and agro ecological processes we focus on policies involving the most prominent crops in the places where biofuel production has advanced the most i e usa brazil and the eu but also extend analysis to their relations with broader transformations in production commercial and even governance practices around the world we investigate the political and economic interests driving biofuel policies and how these set the terms in which state interventions and policies are conceived and implemented we find that these are not developed and implemented according to environmental or inclusive pro poor development purposes but according to state interests in energy security and its intersection with a tense alliance between corporate sectors rendering many policy mechanisms ineffective or even outright counterproductive to effectively facilitate more socially and environmentally sustainable energy production and agricultural practices

manipulation through bribes we consider allocation rules that choose outcomes and transfers based on agents reported valuations of the outcomes a bribing situation exists when one agent could pay another to misreport his valuations resulting in a net gain to both a bribe proof rule eliminates such opportunities we show that under a bribe proof rule each agent s payoff is a continuous function of other agents reported valuations furthermore on connected domains if the set of outcomes is finite or the domain is smoothly connected each agent s payoff is a constant function of other agents reports finally under a domain richness condition a bribe proof rule must be constant the results apply to a broad class of economies journal of economic literature classification numbers c70 d70

forecasting stock return variance toward an understanding of stochastic implied volatilities we examine the behavior of measured variances from the options market and the underlying stock market under the joint hypotheses that markets are informationally efficient and that option prices are explained by a particular asset pricing model forecasts from time series models of the stockreturn process should not have predictive content given the market forecast as embodied in option prices both in sample and out of sample tests suggest that this hypothesis can be rejected using simulations we show that biases inherent in the procedure we use to imply variances cannot explain this result thus we provide evidence inconsistent with the orthogonality restrictions of option pricing models that assume that variance risk is unpriced these results also have implicationsfor optimal variance forecast rules

erm realignment risk and its economic determinants as reflected in cross rate options this paper uses data on over the counter options between the mark and the pound lira french franc and peseta to investigate the credibility of exchange rate target zones within the erm we compare empirical implications for the relation between option prices and the spot s position within the band for three classes of target zone models those with full credibility those with exogenous realignment risk and those with endogenous realignment risk empirically implied volatility from these options attains a maximum near the edges of an exchange rate band rather than its centre even three to six months prior to realignment

predicting volatility in the foreign exchange market measures of volatility implied in option prices are widely believed to be the best available volatility forecasts in this article we examine the information content and predictive power of implied standard deviations isds derived from chicago mercantile exchange options on foreign currency futures the article finds that statistical time series models even when given the advantage of ex post parameter estimates are outperformed by isds isds however also appear to be biased volatility forecasts using simulations to investigate the robustness of these results the article finds that measurement errors and statistical problems can substantially distort inferences even accounting for these however isds appear to be too variable relative to future volatility it is widely believed that the volatility implied in option prices is the market s best estimate of future volatility after all if it were not one could devise a trading strategy that could generate profits by identifying mispriced options the purpose of this article is to investigate the information content and predictive power of volatility implied in options on foreign currencies the paper focuses on options on currency futures traded on the chicago mercantile exchange cme because of the depth and liquidity of cme futures and options traded side by side in the same market implied standard deviations isds allow for clean tests of the predictive power of implied volatilities early studies of the information content of isds have generally found that these contain substantial information for future volatility latane and rendleman 1976 chiras and manaster 1978 and beckers 1981 for example regress future volatility on the weighted implied volatility across a broad sample of chicago board options exchange cboe stocks and find that options contain volatility forecasts that are more accurate than historical measures 1 these studies performed shortly after the 1973 beginning of the cboe option market could only use a relatively short time span and therefore focused on cross sections rather than time series predictions

an options based analysis of emerging market exchange rate expectations brazil s real plan 1994 1999 abstract this paper uses currency option data to investigate market expectations on the brazilian real u s dollar exchange rate from october 1994 through march 1999 we derive implied probability density functions pdf for expected future exchange rates and thus measures of the credibility of the crawling peg and target zone regimes governing the exchange rate target zone credibility was poor prior to february 1996 improved afterwards through september 1997 and later started to worsen again the market anticipated periodic band adjustments and estimated distributions are very sensitive to political and economic news affecting the credibility of the regime

strategyproof assignment by hierarchical exchange we give a characterization of the set of group strategyproof pareto optimal and reallocation proof allocation rules for the assignment problem where individuals are assigned at most one indivisible object without any medium of exchange although there are no property rights in the model the rules satisfying the above criteria imitate a trading procedure with individual endowments in which individuals exchange objects from their hierarchically determined endowment sets in an iterative manner in particular these assignment rules generalize gale s top trading cycle procedure the classical rule for the model in which each individual owns an indivisible good

recovering an asset s implied pdf from option prices an application to crude oil during the gulf crisis we develop a general method for estimating the implied martingale equivalent probability density function pdf for futures prices from american options prices the early exercise feature of american options precludes expressing the price of the option in terms of the pdf there exist tight bounds for the price of american options in terms of the pdf we demonstrate how these bounds together with observed option prices can be used to estimate the parameters of the pdf we estimate the distribution for crude oil during the persian gulf crisis and find the distribution differs significantly from that recovered using standard techniques

individual versus group strategy proofness when do they coincide a social choice function is group strategy proof on a domain if no group of agents can manipulate its final outcome to their own benefit by declaring false preferences on that domain there are a number of economically significant domains where interesting rules satisfying individual strategy proofness can be defined and for some of them all these rules turn out to also satisfy the stronger requirement of group strategy proofness we provide conditions on domains guaranteeing that for all rules defined on them individual and group strategy proofness become equivalent we also provide a partial answer regarding the necessity of our conditions

group incentive compatibility for matching with contracts abstract hatfield and milgrom hatfield john william milgrom paul r 2005 matching with contracts amer econ rev 95 913 935 present a unified model of matching with contracts which includes the standard two sided matching and some package auction models as special cases they show that the doctor optimal stable mechanism is strategy proof for doctors if hospitals preferences satisfy substitutes and the law of aggregate demand we show that the doctor optimal stable mechanism is group strategy proof for doctors under these same conditions that is no group of doctors can make each of its members strictly better off by jointly misreporting their preferences we derive as a corollary of this result that no individually rational allocation is preferred by all the doctors to the doctor optimal stable allocation

assigning refugees to landlords in sweden efficient stable maximum matchings in this paper we investigate the problem of finding housing for refugees once they have been granted asylum in particular we demonstrate that market design can play an important role in a partial solution to the problem more specifically we investigate a specific matching system and we propose an easy to implement mechanism that finds an efficient stable and maximum matching such a matching guarantees that housing is efficiently provided to a maximum number of refugees and that no refugee prefers another specific landlord to their current match when at the same time that specific landlord prefers that refugee to their own current match

obviously strategy proof mechanisms what makes some strategy proof mechanisms easier to understand than others to address this question i propose a new solution concept a mechanism is obviously strategy proof osp if it has an equilibrium in obviously dominant strategies this has a behavioral interpretation a strategy is obviously dominant if and only if a cognitively limited agent can recognize it as weakly dominant it also has a classical interpretation a choice rule is osp implementable if and only if it can be carried out by a social planner under a particular regime of partial commitment i fully characterize the set of osp mechanisms in a canonical setting with one dimensional types and transfers a laboratory experiment tests and corroborates the theory

can we meet targets for biofuels and renewable energy in transport given the constraints imposed by policy in agriculture and energy abstract the deployment of biofuels is significantly affected by policy in energy and agriculture in the energy arena concerns regarding the sustainability of biofuel systems and their impact on food prices led to a set of sustainability criteria in eu directive 2009 28 ec on renewable energy in addition the 10 biofuels target by 2020 was replaced with a 10 renewable energy in transport target this allows the share of renewable electricity used by electric vehicles to contribute to the mix in achieving the 2020 target furthermore only biofuel systems that effect a 60 reduction in greenhouse gas emissions by 2020 compared with the fuel they replace are allowed to contribute to meeting the target in the agricultural arena cross compliance which is part of eu common agricultural policy dictates the allowable ratio of grassland to total agricultural land and has a significant impact on which biofuels may be supported this paper outlines the impact of these policy areas and their implications for the production and use of biofuels in terms of the 2020 target for 10 renewable transport energy focusing on ireland the policies effectively impose constraints on many conventional energy crop biofuels and reinforce the merits of using biomethane a gaseous biofuel the analysis shows that ireland can potentially satisfy 15 of renewable energy in transport by 2020 allowing for double credit for biofuels from residues and ligno cellulosic materials as per directive 2009 28 ec through the use of indigenous biofuels grass biomethane waste and residue derived biofuels electric vehicles and rapeseed biodiesel

il legal assignments in school choice in public school choice students with strict preferences are assigned to schools schools are endowed with priorities over students incorporating constraints from different applications priorities are often modelled as choice functions over sets of students it has been argued that the most desirable criterion for an assignment is stability there should not exist any blocking pair no student shall prefer some school to her assigned school and have higher priority than some student who got into that school or the school has an empty seat we propose a blocking notion where in addition it must be possible to assign the student to her preferred school we then define the following stability criterion for a set of assignments a set of assignments is legal if and only if any assignment outside the set is blocked with some assignment in the set and no two assignments inside the set block each other we show that under very basic conditions on priorities there always exists a unique legal set of assignments and that this set has a structure common to the set of stable assignments i it is a lattice and ii it satisfies the rural hospitals theorem the student optimal legal assignment is efficient and provides a solution for the conflict between stability and efficiency

erm bandwidths for emu and after evidence from foreign exchange options ems credibility exchange rate expectations implied by derivatives prices are the wide bands adopted in the summer of 1993 too large the official answer is that wide bands offer a protection against speculative pressure while exchange rates may be kept within narrower margins at the discretion of the authorities yet if exchange rate fixity and predictability are desirable as implicitly assumed by the mere existence of the system there must exist a trade off between protection against speculative pressure and predictability in that case the bandwidth chosen should be as narrow as possible and yet unlikely to be challenged by the markets this paper offers estimates of safe bandwidths for the long term member currencies french franc peseta danish krone and escudo the existing 15 bands are found to be unnecessarily wide narrower 3 5 bands would capture at least 95 of expected exchange rate realizations over a three month horizon for the lira finnish markka and swedish krone wider bands of 5 6 would capture a similar amount of the exchange rate distribution the pound s exchange rate expectations are the most dispersed requiring 8 4 bands to capture 95 of exchange rate expectations jose m campa p h kevin chang and robert l reider

sugar rush prospects for a global ethanol market in 2005 the major economies of the world including the g8 and 5 developing nations mexico india brazil china and south africa along with the united nations the international energy agency and the european union launched the global bioenergy partnership to discuss ways to promote the sustained use and production of biofuels around the globe reflecting growing concerns for finding economically viable substitutes for petroleum this paper examines whether and if a vibrant global market in biofuels based on sugarcane based ethanol is economically feasible the paper finds that while there is already international trading in biofuels it is highly limited compared with its potential in the current climate of accelerating fossil fuel prices biofuels represent an increasingly attractive displacement for some of our fossil fuel addiction not only do they substitute for petrol but they also produce lower emissions the paper finds that sugarcane ethanol could make an important contribution to substituting for a portion of petroleum and also offer potential benefits for international development

stochastic devaluation risk and the empirical fit of target zone models in the model of this paper an exchange rate fluctuates between given boundaries for random lengths of time and jumps discretely when devaluation occur we provide explicit solutions for the stochastic processes followed by the exchange rate and by the expected rate of depreciation when the likelihood and the size of devaluations vary stochastically over time the model produces realistic patterns of covariation between exchange rates and interest rate differentials and provides interesting interpretations of available empirical evidence we also specify how to infer devaluation risk from target zone data

group strategy proofness in private good economies many salient rules to allocate private goods are not only strategyproof but also group strategy proof in appropriate domains of definition hence diminishing the traditional conflict between incentives and efficiency that is so for solutions to matching division cost sharing house allocation and auctions in spite of the substantive disparity between these cases in a general framework encompassing all of them we prove that the equivalence between the two forms of strategy proofness is due to an underlying common structure that transcends the many differences between the contexts and the mechanisms for which it holds jel c78 d44 d63 d71 d82

modeling heteroscedasticity in daily foreign exchange rates this article estimates autoregressive conditionally heteroscedastic arch and generalized arch garch models for five foreign currencies using 10 years of daily data a variety of arch and garch specifications a number of nonnormal error densities and a comprehensive set of diagnostic checks it finds that arch and garch models can usually remove all heteroscedasticity in price changes in all five currencies goodness of fit diagnostics indicate that exponential garch with certain nonnormal distributions fits the canadian dollar extremely well and the swiss franc and the deutsche mark reasonably well only one nonnormal distribution fits the japanese yen reasonably well none fit the british pound

implied exchange rate distributions evidence from otc option markets abstract this paper uses a rich new dataset of option prices on the dollar mark dollar yen and key ems cross rates to extract the entire risk neutral probability density function pdf over horizons of 1 and 3 months we compare three alternative smoothing methods cubic splines an implied binomial tree trimmed and untrimmed and a mixture of lognormals for transforming option data into the pdf despite their methodological differences the three approaches lead to a similar pdf clearly distinct from the lognormal benchmark and typically characterized by skewness and leptokurtosis we then document a striking positive correlation between skewness in these pdfs and the spot rate the stronger a currency the more expectations are skewed towards a further appreciation of that currency we interpret this finding as a rejection that innovations in these exchange rates are independent of the level or characteristic of a credible target zone explicit or implicit instead this positive correlation is consistent with target zones with endogenous realignment risk we discuss two interpretations of our results on skewness when a currency is stronger the actual probability of further large appreciation is higher or because of risk such states are valued more highly

matching with contracts we develop a model of matching with contracts which incorporates as special cases the college admissions problem the kelso crawford labor market matching model and ascending package auctions we introduce a new law of aggregate demand for the case of discrete heterogeneous workers and show that when workers are substitutes this law is satisfied by profit maximizing firms when workers are substitutes and the law is satisfied truthful reporting is a dominant strategy for workers in a worker offering auction matching algorithm we also parameterize a large class of preferences satisfying the two conditions

coalitional strategy proof house allocation abstract we consider house allocation without endowments we show that there is a unique maximal domain including all strict preferences on which efficiency and coalitional strategy proofness are compatible a preference relation belongs to the unique maximal domain if it is a strict descending ranking of houses to a certain house and indifference holds over it and the remaining houses we also show that on this domain mixed dictator pairwise exchange rules are the only rules satisfying efficiency and coalitional strategy proofness journal of economic literature classification numbers c78 d63 d71

tests of an american option pricing model on the foreign currency options market this paper tests the ability of the american option pricing model proposed by parkinson 18 or mason 14 to explain the pricing of the foreign currency options traded on the philadelphia stock exchange from february 28 1983 to march 26 1985 we find that the model underprices out of the money options relative to at the money and in the money options this relative underpricing is driven by an underpricing of out of the money call options of short maturity in addition the degree of relative mispricing for most categories of options is shown to be a decreasing function of the time to maturity of the options longer maturity options appear to trade at similar levels of implied volatility whether they are in at or out of the money most of these biases appear consistent with the fact that the underlying spot currency rate follows a mixed jump diffusion process as described in 17

incentives in the probabilistic serial mechanism abstract the probabilistic serial mechanism bogomolnaia and moulin 2001 9 is ordinally efficient but not strategy proof we study incentives in the probabilistic serial mechanism for large assignment problems we establish that for a fixed set of object types and an agent with a given expected utility function if there are sufficiently many copies of each object type then reporting ordinal preferences truthfully is a weakly dominant strategy for the agent regardless of the number of other agents and their preferences the non manipulability and the ordinal efficiency of the probabilistic serial mechanism support its implementation instead of random serial dictatorship in large assignment problems

strategy proofness and stability of the boston mechanism an almost impossibility result abstract public school systems generally use one of the three competing mechanisms the boston mechanism the deferred acceptance mechanism and the top trading cycle mechanism for assigning students to specific schools although the literature generally claims that the boston mechanism is pareto efficient but neither stable nor strategy proof this study delineates a subset of school priority structures for which it fulfills all three criteria we show that the boston mechanism is stable if and only if it is strategy proof if and only if the priority structure is strongly acyclic however we find that the condition of strong acyclicity is nearly impossible to satisfy any priority structure is quasi cyclic whenever there are two schools whose admission quotas are less than the number of students seeking admission

european union leadership in biofuels regulation europe as a normative power the rapid emergence of the european union eu as a leader in global environmental politics has led many scholars to argue in favour of the eu being a normative power in international relations this paper critically examines the eu s biofuels policy and evaluates whether its attempts to lead by example and shape international practice in this field could support such arguments europe s biofuel policies are evaluated through a sustainable development lens so as to determine the extent to which it has embraced a holistic approach to sustainability while not dismissing that the identity of the eu is indeed an explanatory factor and that normative intentions may well be regarded as a motivating force this study argues that an interest based perspective on international environmental regulation offers a supplementary view of how an actor s preferences for an international regime are shaped by erecting barriers aimed at shielding its own inefficient domestic biofuels production the eu is in essence placing trade competitiveness and economic growth above environmental protection thus permitting sustainability concerns to be addressed only in part

dollar jump fears 1984 1992 distributional abnormalities implicit in currency futures options abstract deutsche mark and yen futures options over 1984 1992 and 1986 1992 respectively are examined for deviations from the lognormal assumption underlying standard option pricing models two methods are used an atheoretic skewness premium and daily estimates of moments using a model for pricing american foreign currency futures options under systematic exchange rate jump risk substantial variation over time is found in all moments including implicit skewness and kurtosis the implicit abnormalities predict future abnormalities in log differenced dm futures prices but not yen the peso problem implications do not explain standard rejections of uncovered interest parity

strategy proof and symmetric social choice functions for public good economies we study economies with one private good and one pure public good and consider the following axioms of social choice functions strategy proofness says that no agent can benefit by misrepresenting his preferences regardless of whether the other agents misrepresent or not and whatever his preferences are symmetry says that if two agents have the same preference they must be treated equally anonymity says that when the preferences of two agents are switched their consumption bundles are also switched individual rationality says that a social choice function never assigns an allocation which makes some agent worse off than he would be by consuming no public good and paying nothing in theorem 1 we characterize the class of strategy proof budget balancing and symmetric social choice functions assuming convexity of the cost function of the public good in theorem 2 we characterize the class of strategy proof budget balancing and anonymous social choice functions in theorem 3 we characterize the class of strategy proof budget balancing symmetric and individually rational social choice functions

generating options implied probability densities to understand oil market events abstract we investigate the informational content of options implied probability density functions pdfs for the future price of oil using a semiparametric variant of the methodology in breeden and litzenberger 1978 we investigate the fit and smoothness of distributions derived from alternative pdf estimation methods and develop a set of robust summary statistics using pdfs estimated around episodes of high geopolitical tensions oil supply disruptions macroeconomic data releases and shifts in opec production strategy we explore the extent to which oil price movements are expected or unexpected and whether agents believe these movements to be persistent or temporary