on the exclusion of assets from tests of the mean variance efficiency of the market portfolio this paper presents an analysis of the testability of the mean variance efficiency of a market index when the returns on some components of the index itself are not perfectly observable the results are basically not supportive of the notion that mean variance efficiency is testable on a subset of the assets bounding the market share of the missing asset and its expected return is not sufficient to produce a valid test when the variance of the missing asset is bounded and the amount of wealth that might be missing is small it is possible in principle to reject correctly the mean variance efficiency of a market index in his famous critique of the asset pricing theory tests roll 7 concludes that the only testable hypothesis associated with the generalized two parameter asset pricing model of black 1 is that the market portfolio is mean variance efficient it has been emphasized by ross 10 and roll 7 that the mean variance efficiency of the market portfolio is mathematically equivalent to a positive linear relation between expected returns and the betas calculated against such a portfolio roll 7 deduces that the theory capm is not testable unless the exact composition of the market portfolio is known and used in the tests this implies that the theory is not testable unless all individual assets are included in the sample errors of type one or two might occur when a market proxy is used instead of the true market portfolio even if the ex ante true expected returns and the covariance variance matrix of the returns on all the assets are used these errors are the result of the choice of the portfolio and as roll puts it even a small misspecification of the proxy s composition can lead to the wrong conclusion the market proxy might be mean variance efficient while the true market portfolio is not and vice versa in principle however there are cases in which the above two conditions are not both necessary to reject the theory one such exception presented by roll 7 is the case in which no totally positive portfolio is efficient if any totally positive market proxy is used a large sample would reject the null hypothesis unambiguously while the market portfolio identification problem constitutes a severe limitation to the testability of the theory the question of the mean variance efficiency of a particular market index with respect to a subset of assets is a typical problem of statistical inference the mean variance efficiency can be tested directly or by

a theory of disagreement in repeated games with bargaining this paper proposes a new approach to equilibrium selection in repeated games with transfers supposing that in each period the players bargain over how to play although the bargaining phase is cheap talk following a generalized alternating offer protocol sharp predictions arise from three axioms two axioms allow the players to meaningfully discuss whether to deviate from their plan the third embodies a theory of disagreement that play under disagreement should not vary with the manner in which bargaining broke down equilibria that satisfy these axioms exist for all discount factors and are simple to construct all equilibria generate the same welfare optimal play under agreement generally requires suboptimal play under disagreement whether patient players attain efficiency depends on both the stage game and the bargaining protocol the theory extends naturally to games with imperfect public monitoring and heterogeneous discount factors and yields new insights into classic relational contracting questions

communicating subjective evaluations consider managers evaluating their employees performances should managers justify their subjective evaluations suppose a manager s evaluation is private information justifying her evaluation is costly but limits the principal s scope for distorting her evaluation of the employee i show that the manager justifies her evaluation if and only if the employee s performance was poor the justification assures the employee that the manager has not distorted the evaluation downwards for good performance however the manager pays a constant high wage without justification the empirical literature demonstrates that subjective evaluations are lenient and discriminate poorly between good performance levels this pattern was attributed to biased managers i show that these effects occur in optimal contracts without any biased behavior

a theory of contracts with limited enforcement we present a theory of contracts under costly enforcement in the context of a dynamic relationship between an uninformed buyer and a seller who is privately informed on his persistent cost at the outset public enforcement relies on remedies for breach private enforcement comes from severing relationships we first characterize aggregate enforcement constraints ensuring that trading partners do not breach contracts unduly whether a long term contract is enforceable does not depend on the distribution of penalties for breach between the buyer and the seller while under complete information the optimal contract would remain stationary non stationarity might arise under asymmetric information enforcement constraints are time dependent and easier to satisfy as time passes indeed a high cost seller may be tempted to trade high volumes at high prices at the beginning of the relationship before breaching the contract later on yet such take the money and run strategy becomes less attractive as time passes and can be prevented with backloaded payments the optimal contract thus goes through two different phases first quantities and prices increase at the inception of the relationship later on the contract looks more stationary the public and private sides of enforcement plays different roles in determining the length of the earlier phase of contracting long run screening distortions encapsulate the quality of enforcement offering de facto a link between the quality of the legal system and contractual performances

incomplete contracts and strategic ambiguity why are observed contracts so often incomplete in the sense that they leave contracting parties obligations vague or unspecified traditional answers to this question invoke transaction costs or bounded rationality in contrast the authors argue that such incompleteness is often an essential feature of a well designed contract specifically once some aspects of performance are unverifiable it is often optimal to leave other verifiable aspects of performance unspecified the authors explore the conditions under which this occurs and investigate the structure of optimal contracts when these conditions are satisfied copyright 1998 by american economic association

the statistical properties of daily foreign exchange rates 1974 1983 abstract this paper examines the statistical properties of daily rates of change of five foreign currencies from 1974 to 1983 the main purpose is to discriminate between two competing explanations for the observed heavy tails of the distribution that the data are independently drawn from a heavy tail distribution which remains fixed over time and that the data come from distributions which vary over time evidence point to the rejection of the first hypothesis further investigations show that the rejection can be attributed to changing means and variances in the data which can be described by a simple statistical model

in search of the exchange risk premium a six currency test assuming mean variance optimization abstract a number of authors examining deviations of actual rates of currency depreciation from forward discounts have claimed to find evidence of risk premiums if these deviations are indeed partly due to risk premiums rather than being entirely due to expectational errors then they should be systematically related to those variables on which risk premiums are thought to depend finance theory tells us that if investors optimize with respect to mean and variance the risk premium depends in a specific way on 1 the supplies of assets denominated in the various currencies 2 the variance covariance matrix of the rates of return and 3 the coefficient of risk aversion the null hypothesis of this paper is that the coefficient of risk aversion is zero countries assets are perfect substitutes and risk premiums are nonexistent the alternative hypothesis is that rates of return are systematically related to asset supplies by a macroeconomic portfolio balance function the maximum likelihood technique used dominates previous attempts to find such a relationship in that the parameters of the portfolio balance function are constrained to depend on the variance covariance matrix as the finance theory says they should on the other hand the technique also dominates previous applications of the finance theory in that the expected returns are allowed to vary over time as the macroeconomic portfolio balance theory says they should the paper s finding is a statistical inability to reject the null hypothesis for a portfolio of six currencies although this could be due to low power in the test

even up maintaining relationships abstract when are economic interactions mediated by prices and transfers and when are they mediated by variations in the continuation payoffs within a relationship to address this question we examine a relationship between two players who periodically face opportunities to undertake randomly generated projects that impose a cost on one player and a benefit on the other as well as opportunities to make voluntary transfers to one another we characterize the set of equilibria with particular emphasis on the efficient frontier in the absence of transfers incentives are often created by adjusting the continuation values of the relationship sometimes increasing player 1 s continuation payoff to induce player 1 to accept a particularly costly current project and sometimes increasing player 2 s continuation payoff in contrast once transfers enter the picture continuation payoffs maximize the sum of the two players payoffs no matter how asymmetric the point on the pareto frontier under consideration however transfers can also be relatively rare and in particular can occur less often than the adjustments in continuation values that occur without transfers players thus rely on transfers to create incentives but manage to do so while rarely making transfers

subjective performance measures in optimal incentive contracts objective measures of performance are seldom perfect in response incentive contracts often include important subjective components that mitigate incentive distortions caused by imperfect objective measures this paper explores the combined use of subjective and objective performance measures in respectively implicit and explicit incentive contracts naturally objective and subjective measures often are substitutes sometimes strikingly so we show that if objective measures are sufficiently close to perfect then no implicit contracts are feasible because the firm s fallback position after reneging on an implicit contract is too attractive we also show however that objective and subjective measures can reinforce each other if objective measures become more accurate then in some circumstances the optimal contract puts more weight on subjective measures because the improved objective measures increase the value of the ongoing relationship and so reduce the firm s incentive to renege we also analyze the use of subjective weights on objective performance measures and provide case study evidence consistent with our analyses

a note on exchange rate expectations and nominal interest differentials a test of the fisher hypothesis this note tests the hypothesis that nominal interest differentials between similar assets denominated in different currencies can be explained entirely by the expected change in the exchange rate over the holding period this proposition often called the fisher open hypothesis or the hypothesis of perfect asset substitutability has been a major component of recent theories of exchange rate determination and has important implications for monetary policy 1 the fisher hypothesis differs from the covered interest parity theorem enunciated by keynes 11 while covered interest parity equates the nominal interest differential between financial centers to a known premium or discount on forward foreign exchange and is thus in principle riskless fisher parity involves risk in an essential way the two conditions are equivalent only when forward exchange rates equal expected future spot rates recent theoretical work for example that of grauer litzenberger and stehle 8 kouri 12 and frankel 6 shows that this need not be the case when market participants are risk averse thus while covered interest parity must always hold exactly in an informationally efficient asset market with no transactions costs fisher parity need not nominal interest differentials may reflect risk premia in addition to expected exchange rate movements 2 it should be emphasized at the outset that the tests conducted in this paper are really joint tests of the fisher hypothesis and a weak form of foreign exchange market informational efficiency levich 14 has argued that tests of market efficiency are always joint tests involving some hypothesized structure of normal equilibrium returns below we assume informational efficiency and instead test fisher s hypothesized arbitrage condition that nominal interest differentials equal expected percentage changes in exchange rates

the existence of self enforcing implicit contracts implicit contracts are nontrivial nash equilibria to the post hiring trading game between a worker and the employer these are supported by intrafirm rather than labor market reputations the existence of an implicit contract that supports efficient trade is proved in a simple model

the interaction of implicit and explicit contracts in repeated agency abstract in a repeated principal agent model in which the agent s actions are observable to the principal but not verifiable in court the agent s incentives derive both from salary payments based on verifiable signals and from implicit promises by the principal of bonuses for good behavior explicit short term contracts are designed to enhance the effectiveness of the infinite horizon implicit contract between principal and agent in a constrained efficient equilibrium bonuses smooth the consumption path of the risk averse agent by moving in the opposite direction from salaries total consumption and expected discounted utility for the rest of the game journal of economic literature classification numbers c7 c73 d8

contracting with repeated moral hazard and private evaluations a repeated moral hazard setting in which the principal privately observes the agent s output is studied the optimal contract for a finite horizon is characterized and shown to require burning of resources these are only burnt after the worst possible realization sequence and the amount is independent of both the length of the horizon and the discount factor for the infinite horizon it is shown that there is no loss from restricting the analysis to contracts in which the agent receives a constant efficiency wage and no feedback until he is fired furthermore optimal contracts cannot be replicated by short term contracts a family of fixed interval review contracts is characterized longer review intervals are preferable but harder to implement comparative statics on the review length are carried out finally these contracts are shown approximate first best if players are very patient jel d82 d86

the economic impact of minimum wages in europe opponents of minimum wages argue that they hurt jobs in europe supporters say that they combat exploitation and help the poor we try to sort out myth from reality differing policy prescriptions reflect different views of how the labour market actually works contrary to popular wisdom it is as easy to make a theoretical case against minimum wages as for them evidence not theory is what is needed now relative to average wages minimum wages have not risen in europe over the last 30 years they caused higher unemployment only if they prevented a necessary fall in the wages of the low paid second minimum wages for young workers are often a lower proportion of average earnings in europe than in the usa third we find no general evidence that minimum wages reduced employment except perhaps for young workers the good or bad effect of minimum wages has been exaggerated

discretionary rewards as a feedback mechanism abstract this paper studies the use of discretionary rewards in a finitely repeated principal agent relationship with moral hazard the key aspect is that rewards have informational content when the principal obtains a private subjective signal about the agent s performance she may pay discretionary bonuses to provide credible feedback to the agent in accordance with the often observed compression of ratings we show that in equilibrium the principal communicates the agent s interim performance imperfectly i e she does not fully differentiate good and bad performance furthermore we show that small rewards can have a large impact on the agent s effort provided that the principal s stake in the project is small

renegotiation and conflict resolution in relational contracting abstract renegotiation and conflict resolution are studied in relational contracting under subjective evaluation renegotiation has three effects first it makes the incentive pay scheme low powered the maximum variation of compensation across performance levels is compressed and the contract is less extreme compared to the case without renegotiation this effect is stronger when the players are less patient second renegotiation typically renders termination impossible the contract relies on a low morale mechanism to enforce mutual cooperation finally renegotiation compels the players to resolve their conflicts by selecting a contract that maximizes the lowest possible surplus along the path of the contract

relational incentive contracts standard incentive theory models provide a rich framework for studying informational problems but assume that contracts can be perfectly enforced this paper studies the design of self enforced relational contracts i show that optimal contracts often can take a simple stationary form but that self enforcement restricts promised compensation and affects incentive provision with hidden information it may be optimal for an agent to supply the same inefficient effort regardless of cost conditions with moral hazard optimal contracts involve just two levels of compensation this is true even if performance measures are subjective in which case optimal contracts terminate following poor performance jel c73 d82 l14

subjective performance indicators and discretionary bonus pools key indicators of managerial performance are frequently subjective that is they are difficult to specify and or verify for contracting purposes when a principal must rely on subjective information to create incentives for a group of agents discretionary bonus pools are shown to be optimal mechanisms despite their optimality however discretionary bonus pools entail an additional agency cost relative to the benchmark of optimal contracts based on objective and verifiable information our analysis identifies circumstances under which this additional agency cost is small for example the subjective information signals are precise or the number of agents participating in the bonus pool increases when incentive schemes can be based on both objective and subjective performance indicators the relative weights to be placed on alternative signals are shown to differ from the ones predicted by models with objective signals only we also demonstrate that correlation in measurement errors has a different impact on the structure of optimal incentive schemes when the performance indicators are merely subjective

endogenous and exogenous commitment abstract i study a dynamic model of monopoly sales in which one long term monopolist without exogenous commitment power interacts with a sequence of short term consumers with private valuations i provide a folk theorem which characterizes the payoffs of a sufficiently patient monopolist and i show that exogenous commitment power can obstruct the endogenous commitment from repeated game incentives

the folk theorem with imperfect public information the authors study repeated games in which players observe a public outcome that imperfectly signals the actions played they provide conditions guaranteeing that any feasible individually rational payoff vector of the stage game can arise as a perfect equilibrium of the repeated game with sufficiently little discounting the central condition requires that there exist action profiles with the property that for any two players no two deviations one by either player give rise to the same probability distribution over public outcomes the results apply to principal agent partnership oligopoly and mechanism design models and to one shot games with transferable utilities copyright 1994 by the econometric society

credence goods costly diagnosis and subjective evaluation we study contracting between a consumer and an expert the expert can invest in diagnosis to obtain a noisy signal about whether a low cost service is sufficient or whether a high cost treatment is required to solve the consumer s problem this involves moral hazard because diagnosis effort and signals are not observable treatments are contractible but success or failure of the low cost treatment is observed only by the consumer payments can therefore not depend on the objective outcome but only the consumer s report or subjective evaluation a failure of the low cost treatment delays the solution of the consumer s problem by the high cost treatment to a second period we show that the first best solution can always be implemented if the parties discount rate is zero an increase in the discount rate reduces the range of parameter combinations for which the first best can be obtained in an extension we show that the first best is also always implementable if diagnosis and treatment can be separated by contracting with two different agents

on the exclusion of assets from tests of the mean variance efficiency of the market portfolio an extension this paper extends kandel s 3 analysis of the testability of the mean variance efficiency of a market index when the return on some component of the index is not perfectly observable in addition to information about the mean and variance of the missing asset considered by kandel we explore the usefulness of information about the beta of the missing asset on the observed sub portfolio in an economy with a riskless asset the results are somewhat more supportive of the notion that mean variance efficiency is testable on a subset of the assets in his important critique of tests of the capital asset pricing model roll 4 emphasizes that empirical results obtained with market proxies need not be indicative of the results that would be obtained in testing the efficiency of the true market portfolio were it observable more recently kandel 3 has analyzed the testability of the mean variance efficiency of a market portfolio when the return on some component of the portfolio is not perfectly observable but partial information about its characteristics is available he finds that knowledge of the market share and expected return of the missing asset is not sufficient to permit a test however bounding the variance of return on the missing asset does make it possible in principle to correctly reject the efficiency of the portfolio provided that the market share of the missing asset is not too large building on the analytical framework established by kandel we explore the value of information about the riskless rate of return and the covariance betwen the return on the missing asset and the observed sub portfolio given a riskless asset the question we address is whether the unobservable market portfolio of risky assets is equal to the tangency portfolio of the efficient frontier we find that knowledge of the market share and expected return of the missing asset is still not sufficient to permit a test of this more restrictive efficiency condition as in the no riskless asset case given a bound on the variance of the missing asset it is sometimes possible to correctly infer that the unobserved portfolio is inefficient this occurs when the market share of the missing asset or the variance of its return is small and the sub portfolio is sufficiently far from the linear

procurement and renegotiation parties bound by an incomplete contract have an incentive to renegotiate after acquiring new information the issue of the parties investment in the relationship before renegotiation is analyzed in a simple two period procurement model the firm invests in the first period it then learns its production cost and the sponsor learns its value for the project williamson s underinvestment presumption is shown to hold under very general assumptions about bargaining and about the ex post asymmetry of information as long as the firm s investment is not observable by the sponsor the introduction of a cancellation fee may well lead to even less investment contrary to what is sometimes argued the role of ex ante price fixing as an alternative way to reintroduce some form of commitment and the problem of cost overruns are discussed last it is shown that if investment is observable by the sponsor andthus may become a joint decision variable the two parties may choose to under or overinvest

empirical models of the exchange rate separating the wheat from the chaff various popular exchange rate models a standard monetary model a portfolio balance model and sticky price models are estimated and evaluated using u s canadian data for the 1970s nonnested hypothesis tests demonstrate that none are correctly specified the data suggest 1 the exchange rate persistence observed is not fully explained by any of the models 2 the small durbin watson statistics indicate longer lags are required 3 the current account is a useful explanatory variable 4 the portfolio balance model fits the data well but has potentially serious problems measuring the stock of foreign assets this abstract was borrowed from another version of this item

short term contracts and long term agency relationships abstract long term contracts are valuable only if optimal contracting requires commitment to a plan today that would not otherwise be adopted tomorrow we show that commitments are unnecessary and hence short term contracts are sufficient if 1 all public information can be used in contracting 2 the agent can acess a bank on equal terms with the principal 3 recontracting takes place with common knowledge about technology and preferences and 4 the frontier of expected utility payoffs generated by the set of incentive compatible contracts is downward sloping at all times

multivariate proxies and asset pricing relations abstract a framework is developed in which inferences can be made about the validity of an equilibrium asset pricing relation even though the central aggregate in this relation is unobservable a multivariate proxy for the true market portfolio consisting of an equal weighted stock index and a long term government bond index is employed in an investigation of the sharpe lintner capm the empirical evidence suggests that we can reject the joint hypothesis that a capm is valid and b multiple correlation between the true market portfolio and proxy assets exceeds 0 7 connections to the equilibrium factor pricing literature are also explored

endogenous verifiability and relational contracting for contracting parties it will often be uncertain whether a legal court is able to enforce the real intents of their contract the strict requirements of verifiability make it costly if not impos sible for parties to arrange their transactions and design their contract in a way that makes it completely protected by the court a way out is then to rely on self enforcing relational con tracts through repeated transactions the parties can make it costly for each other to breach the contract by letting breach ruin future trade but the self enforcing range of contracts is limited so the court s ability to enforce a contract is not without consequence for the contracting parties if possible the parties may thus have incentives to take costly actions that affect the ability of the court both ex ante preparations in terms of detailed contracting and ex post revelation of informa tion can increase the probability of fair court enforcement in this paper we focus on the former assuming that the parties are able to improve the verifiability of the contracted actions by care ful ex ante contract specifications we assume that careful contracting can improve the court s ability to verify whether an action conforms to the one described in the contract then we ask what happens to the self enforcing contract equilibrium if a party takes actions ex ante that affect the probability of verification in order to provide some answers we analyze a simple repeated principal agent game where the verifiability of the agent s actions is endogenously determined by the principal s investments in drafting an explicit contract pertaining to the quality of the agent s output the model makes it possible to identify some subtle effects of two key enforcement devices legal courts and repeated interaction note that by endogenizing verifiability we also endog enize the degree of contractual incompleteness and the equilibrium level of incompleteness will depend on the verification technology i e the resource costs that are necessary to achieve various verifiability levels this verification technology will be influenced in an essential way by the quality of courts in fact we can use the model to study relationships between two distinct aspects of courts namely their ability which influences the verification technology and their predictability which manifests itself in the equilibrium level of verifiability i e the probability with which the court in fact will verify the relevant action the repeated game approach formalizes an economic concept of trust and trustworthiness since a party honors trust if the present value of honoring exceeds the present value of abusing it the discount factor is then a proxy for the trust level in the relationship by studying the effect of variations in verification technology and the discount factor we can gain insight into the rela tionship between court ability explicit contracting trust and relational contracting below we summarize the results

enforcement of implicit employment contracts through unionization in a world in which employment contracts are incomplete it is costly for a firm to establish credibility for honoring implicit terms of employment agreements by monitoring the employment relationships between the firm and its workers the labor union may provide the workforce with valuable information regarding the firm s adherence to these implicit agreements thus the union provides a signaling mechanism that allows workers to coordinate their actions in order to discipline the firm for a breach of the implicit contract this mechanism enhances the firm s credibility when forming employment contracts and facilitates increased employment levels

optimal cartel equilibria with imperfect monitoring abstract there exist optimal symmetric equilibria in the green porter model 4 8 having an elementary intertemporal structure such an equilibrium is described entirely by two subsets of price space and two quantities the only production levels used by firms in any contingency the central technique employed in the analysis is the reduction of the repeated game to a family of static games

optimal contracting with subjective evaluation this paper extends the standard principal agent model to allow for subjective evaluation the optimal contract results in more compressed pay relative to the case with verifiable performance measures moreover discrimination against an individual implies lower pay and performance suggesting that the extent of discrimination as measured after controlling for performance may underestimate the level of true discrimination finally the optimal contract entails the use of bonus pay rather than the threat of dismissal hence neither efficiency wages nor the right to dismiss an employee are necessary ingredients for an optimal incentive contract

an international capm for bonds and equities abstract previous empirical studies of international capm models have not found much supporting evidence in this paper we suggest reasons why this might have happened and perform new tests using improved models and data a range of monthly capm models are estimated for 1973 1987 for aggretate equities and bonds in germany japan the us and uk the models are an improvement on earlier work in that we integrate equity markets into the analysis instead of focusing exclusively on government bond stocks and we carefully measure the rates of return for both bonds and equities in particular bond returns reflect changes in the price of bonds as well as coupons despite this wider portfolio and the introduction of arch effects in the conditional covariance matrix of errors our model still yields unlikely estimates of the coefficient of relative risk aversion and provides very little explanatory power for expected relative rates of return correcting the icapm for these major deficiencies does not reverse earlier conclusions in the literature a close examination of the residuals of the estimated equations suggest that garch models are not required for our new data set jel fh

relational knowledge transfers an expert must train a novice the novice initially has no cash so he can only pay the expert with the accumulated surplus from his production at any time the novice can leave the relationship with his acquired knowledge and produce on his own the sole reason he does not is the prospect of learning in future periods the pro t maximizing relationship is structured as an apprenticeship in which all production generated during training is used to compensate the expert knowledge transfer takes a simple form in the rst period the expert gifts the novice a positive level of knowledge which is independent of the players discount rate after that the novice s total value of knowledge grows at the players discount rate until all knowledge has been transferred the ine ciencies that arise from this contract are caused by the expert s arti cially slowing down the rate of knowledge transfer rather than by her reducing the total amount of knowledge eventually transferred we show that these ine ciencies are larger the more patient the players are finally we study the impact of knowledge externalities across players

incentive provision when contracting is costly we analyse optimal incentive contracts in a model where the probability of court enforcement is determined by the costs spent on contracting the analysis shows that there is no monotonic relationship between contracting costs and incentive intensity and that an increase in contracting costs may lead to higher powered incentives moreover we formulate hypotheses about the relationship between legal systems and incentive provision specifically the model predicts higher powered incentives in common law than in civil law systems we also find that better performance measures may induce lower investments in contracting and potentially lead to lower powered incentives

on correlations and inferences about mean variance efficiency a framework is presented for investigating the mean variance efficiency of an unobservable portfolio based on its correlation with a proxy portfolio a sensitivity analysis derives the highest correlation between the proxy and a portfolio that reverses the inference of a test of sharpe lintner tangency for example the maximum correlation between the value weighted nyse amex portfolio and a portfolio inferred tangent ranges from 0 76 to 0 48 we also test whether the correlation between the proxy and the tangent portfolio exceeds a given level this hypothesis is often rejected for the nyse amex proxy at a correlation of 0 7

international arbitrage pricing theory an empirical investigation in this paper we test the arbitrage pricing theory apt in an international setting inter battery factor analysis is used to estimate the international common factors and the chow test is used in testing the validity of the apt our inter battery factor analysis results show that the number of common factors between a pair of countries ranges from one to five and our cross sectional test results lead us to reject the joint hypothesis that the international capital market is integrated and that the apt is internationally valid our results however do not rule out the possibility that the apt holds locally or regionally in segmented capital markets finally the basic results of both the inter battery factor analysis and the cross sectional tests are largely invariant to the nume raire currency chosen numerous authors notably solnik 21 grauer litzenberger and stehle 11 and stulz 24 have derived various versions of the international asset pricing model iapm under alternative views of the structure of international capital markets however only a few serious attempts have been made to test various versions of the iapm these tests are largely inconclusive see solnik 20 and stehle 23 apart from the problem stressed by roll 16 of identifying the world market portfolio previous tests of the iapms suffer from the technical problem of aggregating assets of national investors using different numeraire currencies differences in the numeraire arise from differences in consumption baskets in an environment characterized by exchange rate uncertainty in a fruitful attempt to extend the arbitrage pricing theory apt of ross 18 to an international setting solnik 22 derives an international arbitrage pricing theory which is largely devoid of the aforementioned difficulties and thus more amenable to empirical testing 1 as shown by solnik testability of the apt in an

relational incentives and moral hazard in teams this paper studies moral hazard in teams using a model where efforts are promoted via the combination of profit shares and relational contracts the focus is on how these two forms of incentives interact according to the degree of effort observability and the importance of future interaction the optimal allocation of profit shares can range from a wide dispersion across players to a full concentration of shares in the hands of a single player when shares are sufficiently concentrated the corresponding residual claimant can also adopt the role of administering all relational contracts therefore serving as an endogenously chosen principal copyright 2007 wiley blackwell

on repeated moral hazard with discounting in this paper we analyze optimal contracts in an infinitely repeated agency model in which both the principal and agent discount the future we show that there is a stationary representation of the optimal contract when the agent s conditional discounted expected utility is used as a state variable this representation reduces the multi period problem to a static variational problem which can be analyzed using standard variational techniques this reduction is used to obtain several properties of the contract

implicit contracts incentive compatibility and involuntary unemployment this paper considers the enforceability of employment contracts when employees performance cannot be verified in court so that piece rate contracts are not legally enforceable part i shows that there exists a variety of self enforcing implicit contracts modelled as perfect equilibria in a repeated game and characterizes all the wage and performance outcomes that can be implemented implementation requires a strictly positive surplus from employment the form of the contract depending on how this surplus is divided between firm and employee piece rate contracts and contracts with an informally agreed bonus can be made self enforcing but the use of severance pay and bonding does not extend the set of implementable allocations the resulting contracts resemble actual labor contracts more than do the contracts in standard principal agent models part ii analyses market equilibrium with these contracts also modelled as perfect equilibria in a repeated game and shows that many such equilibria exist unfilled vacancies and unemployed workers can co exist despite the existence of contracts that are potentially mutually beneficial for those jobs that are filled any division of the potential surplus is possible so that the market can have at the same time involuntary unemployment and vacancies that are unfilled despite filled jobs earning positive profits as a criterion for selecting equilibria a notion of renegotiation proofness is applied then either all workers are employed or all jobs filled but any division of the potential surplus is still possible the paper explores what further restrictions on beliefs give rise to a walrasian outcome in which all the potential surplus goes to the short side of the market and to an efficiency wage type outcome in which the potential surplus goes to the long side

the multiperiod principal agent problem in repeated principal agent models long term contracts can improve on short term contracts only if they commit either principal or agent to a payoff in some future circumstance lower than could be obtained from a short term contract negotiated if that circumstance occurs we show that efficient contracting under moral hazard alone does not require long term commitment from the principal provided a short term contract can punish the agent sufficiently in a sense made precise it requires no commitment from the agent either then linking payoffs in one period to outcomes in previous periods does not improve the tradeoff between incentives and risk sharing