Paper # Author Title
Economic theory reduces the concept of rationality to internal consistency. The practice of economics, however, distinguishes between rational and irrational beliefs. There is therefore an interest in a theory of rational beliefs, and of the process by which beliefs are generated and justified. We argue that the Bayesian approach is unsatisfactory for this purpose, for several reasons. First, the Bayesian approach begins with a prior, and models only a very limited form of learning, namely, Bayesian updating. Thus, it is inherently incapable of describing the formation of prior beliefs. Second, there are many situations in which there is not sufficient information for an individual to generate a Bayesian prior. Third, this lack of information is even more acute when we address the beliefs that can be attributed to a society. We hold that one needs to explore other approaches to the representation of information and of beliefs, which may be helpful in describing the formation of Bayesian as well as non-Bayesian beliefs. Download Paper
We study transactions that require investments before trading in a competitive market, when forward contracts fixing the transaction price are absent. We show that, despite the market being perfectly competitive and subject to arbitrarily little uncertainty, the inability to jointly determine investment levels and prices may make it impossible for buyers and sellers to predict the prices at which they will trade, leading to inefficient levels of investment and trade. Download Paper
Taller workers receive a wage premium, and the disparity in wages is similarin magnitude to the race and gender gaps. We exploit the variation in an individual's height over time to explore the ways in which height affects wages.Specifically, we show that for white males the effect of adult height is essentially eliminated when adolescent height is taken into account. We find that participation in high school sports and clubs, and to a lesser extent schooling, are channels through which teen height affects adult wages. The benefits of beinga taller teen seem to accrue equally across income classes and also across broad occupation categories, suggesting that the benefits of teen height do not result from occupational sorting. Because height is heritable and because tall adults tend to have children with each other, the benefits of teen height tend to be perpetuated across generations. Finally, we use our estimates of the teen height premium to perform a simple calculation of the monetary benefits of a newly approved treatment for children that increases height. Download Paper
We analyze the ex ante incentive compatible core for replicated private information economies. We show that any allocation in the core when the economy is replicated sufficiently often is approximately Walrasian for the associated Arrow-Debreu economy. Download Paper
We find an economic rationale for the common sense answer to the question in our title — courts should not always enforce what the contracting parties write. We describe and analyze a contractual environment that allows a role for an active court. An active court can improve on the outcome that the parties would achieve without it. The institutional role of the court is to maximize the parties’ welfare under a veil of ignorance. We study a buyer-seller model with asymmetric information and ex-ante investments, in which some contingencies cannot be contracted on. The court must decide when to uphold a contract and when to void it. The parties know their private information at the time of contracting, and this drives a wedge between ex-ante and interim-efficient contracts. In particular, some types pool in equilibrium. By voiding some contracts that the pooling types would like the court to enforce, the court is able to induce them to separate, and hence to improve ex-ante welfare. Download Paper
People may be surprised by noticing certain regularities that hold in existing knowledge they have had for some time. That is, they may learn without getting new factual information. We argue that this can be partly explained by computational complexity. We show that, given a database, finding a small set of variables that obtain a certain value of R2 is computationally hard, in the sense that this term is used in computer science. We discuss some of the implications of this result and of fact-free learning in general. Download Paper
We examine contemporaneous perfect epsilon-equilibria, in which a player's actions after every history, evaluated at the point of deviation from the equilibrium, must be within epsilon of a best response. This concept implies, but is stronger than, Radner's ex ante perfect epsilon-equilibrium. A strategy profile is a contemporaneous perfect epsilon-equilibrium of a game if it is a subgame perfect equilibrium in a perturbed game with nearly the same payoffs, with the converse holding for pure equilibria. Download Paper
We posit that the value of a manager's human capital depends on the firm's business strategy. The resulting interaction between business strategy and managerial incentives affects the organization of business activities, both the internal organization of the firm and the determination of firm boundaries. We illustrate the impact of this interaction on firm boundaries in a dynamic agency model. There may be disadvantages in merging two firms even when such a merger allows the internalization of externalities between the two firms. Merging, by making unprofitable certain decisions, ncreases the cost of inducing managerial effort. This incentive cost is a natural consequence of the manager's business-strategy-specific human capital. Download Paper
We study transactions that require investments before trading in a competitive market, when forward contracts fixing the transaction price are absent. We show that, despite the market being perfectly competitive and subject to arbitrarily little uncertainty, the inability to jointly determine investment levels and prices may make it impossible for buyers and sellers to predict the prices at which they will trade,leading to inefficient levels of investment and trade. Download Paper
We develop an auction model for the case of interdependent values and multidimensional signals in which agents' signals are correlated. We provide conditions under which a modification of the Vickrey auction which includes payments to the bidders will result in an ex post efficient outcome. Furthermore, we provide a definition of informational size such that the necessary payments to bidders will be arbitrarily small if agents are sufficiently informationally small. Download Paper
There is ample evidence that emotions affect performance. Positive emotions can improve performance, while negative ones may diminish it. For example, the fears induced by the possibility of failure or of negative evaluations have physiological consequences (shaking, loss of concentration) that may impair performance in sports, on stage or at school. There is also ample evidence that individuals have distorted recollection of past events, and distorted attributions of the causes of successes of failures. Recollection of good events or successes is typically easier than recollection of bad ones or failures. Successes tend to be attributed to intrinsic aptitudes or own effort, while failures are attributed to bad luck. In addition, these attributions are often reversed when judging the performance of others. The objective of this paper is to incorporate the first phenomenon above into an otherwise standard decision theoretic model, and show that in a world where performance depends on emotions, biases in information processing enhance welfare. Download Paper
In McLean and Postlewaite (2002), we analyzed pure exchange economies with asymetrically informed agents. We defined a notion of informational size and showed that, when the aggregate information of all agents resolves nearly all the uncertainty regarding the state of nature, the conflict between incentive compatibility and (ex post) efficiency can be made small if agents have sufficiently small informational size. This paper investigates the relationship between informational size and efficiency for the case in which nontrivial aggregate uncertainty is present, i.e., when significant uncertainty about the world persists even when the information of all agents is known. We prove the existence of incentive compatible, individually rational and nearly ex post efficient allocations without assuming negligible aggregate uncertainty when agents have small informational size relative to informational variability. We further show that the conflict between incentive compatibility and efficiency asymptotically vanishes when an economy is replicated. Download Paper
The social context can have a large impact on economic decisions. The theoretical challenge is to formulate a model that encompasses both social and economic decisions in a meaningful manner. We discuss the incorporation of social context into neoclassical economic models using social institutions. We also discuss the relationship between social institutions, social capital, and the social value of assets (introduced by Mailath and Postlewaite (2002)). Download Paper
Inductive learning aims at finding general rules that hold true in a database. Targeted learning seeks rules for the prediction of the value of a variable based on the values of others, as in the case of linear or non-parametric regression analysis. Non-targeted learning finds regularities without a specific prediction goal. We model the product of non-targeted learning as rules that state that a certain phenomenon never happens, or that certain conditions necessitate another. For all types of rules, there is a trade-off between the rule's accuracy and its simplicity. Thus rule selection can be viewed as a choice problem, among pairs of degree of accuracy and degree of complexity. However, one cannot in general tell what is the feasible set in the accuracy complexity space. Formally, we show that finding out whether a point belongs to this set is computationally hard. In particular, in the context of linear regression, finding a small set of variables that obtain a certain value of R2 is computationally hard. Computational complexity may explain why a person is not always aware of rules that, if asked, she would find valid. This, in turn, may explain why one can change other people's minds (opinions, beliefs) without providing new information. Download Paper
We develop an auction model for the case of interdependent values and multidimensional signals in which agents' signals are correlated. We provide conditions under which a modification of the Vickrey auction which includes payments to the bidders will result in an ex post efficient outcome. Furthermore, we provide a definition of informational size such that the necessary payments to bidders will be arbitrarily small if agents are sufficiently informationally small. Download Paper
We present a dynamic agency model in which changes in the structure of a firm affect its value due to altered incentives. There may be disadvantages in merging two firms even when such a merger allows the internalization of externalities between the two firms. Merging, by making unprofitable certain decisions, increases the cost of inducing managers to exert effort. This incentive cost arises as a natural consequence of the manager's firm-specific human capital. Download Paper
We present a dynamic agency model in which changes in the structure of a firm affect its value due to altered incentives. There may be disadvantages in merging two firms even when such a merger allows the internalization of externalities between the two firms. Merging, by making unprofitable certain decisions, increases the cost of inducing managers to exert effort. Download Paper
We examine contemporaneous perfect epsilon-equilibria, in which a player's actions after every history, evaluated at the point of deviation from the equilibrium, must be within epsilon of a best response. This concept implies, but is not implied by Radner's ex ante perfect epsilon-equilibrium. A strategy profile is a contemporaneous perfect epsilon-equilibrium of a game if it is a subgame perfect equilibrium in a game achieved by perturbing payoffs by at most epsilon/2, with the converse holding for pure equilibria. Download Paper
We present a model incorporating both social and economic components, and analyze their interaction. We argue that such analysis is necessary for an understanding of the social arrangements that are consistent with underlying economic fundamentals. We introduce the notion of a social asset, an attribute that has value only because of the social arrangements governing society. We consider a generational matching model in which an attribute has value in some equilibrium social arrangements (matching patterns), but not in others. We then show that productive attributes (such as education) can have their value increased above their inherent productive value by some social arrangements, leading to the notion of the social value of an asset. Download Paper
There is ample evidence that confidence can affect performance: confidence can improve performance, while a lack of confidence may diminish it. For example. the fears induced by the possibility of failure or of negative evaluations have physiological consequences (shaking, loss of concentration) that may impair performance in sports, on stage or at school. Download Paper
In McLean and Postlewaite (2001), we analyzed a general equilibrium model with asymmetrically informed agents. We presented a notion of informational size and showed (among other things) that when agents' information as a whole resolved nearly all the uncertainty, the conflict between incentive compatibility and (ex post) efficiency can be made arbitrarily small if agents are sufficiently small informationally. This paper extends the analysis of the relationship between informational size and efficiency to the case in which there is nontrivial aggregate uncertainty, that is, when there is significant uncertainty about the world even when the information of all agents is known. We further show that the conflict between incentive compatibility and efficiency asymptotically vanishes when an economy is replicated. Download Paper
Taller workers receive a wage premium, and the disparity in wages is similar in magnitude to the race and gender gaps. We exploit the variation in an individual's height over time to explore the way in which height affects wages. Specifically, we show that for white males, the effect of adult height is essentially eliminated when adolescent height is taken into account. We take this as evidence that adolescent height has important economic implications long after the time that it is observable to others, and we explore the channels through which the effects might be manifested. Download Paper
We develop an auction model for the case of interdependent values and multidimensional signals in which agents' information is not independent. We show that a modification of the Vickrey auction which includes payments to the bidders will result in an efficient outcome under very good general conditions. Further, we provide a definition of informational size such that the necessary payments to bidders will be arbitrarily small if agents are sufficiently informationally small. Download Paper
We examine a general equilibrium model with asymetrically informed agents. The presence of asymmetric information generally presents a conflict between incentive compatibility and Pareto efficiency. We present a notion of informational size and show that the conflict between incentive compatibility and efficiency can be made arbitrarily small if agents are sufficiently small informationally. Download Paper
We examine the ex ante incentive compatible core, and show that generically, when agents are informationally small in the sense of McLean and Postlewaite (1999), the ex ante incentive compatible core is nonempty. Download Paper
We study a contracting model with unforeseen contingencies in which the court is an active player. Ex-ante, the contracting parties cannot include the risky unforeseen contingencies in the contract they draw up. Ex-post the court observes whether an unforeseen contingency occurred, and decides whether to void or uphold the contract. If the contract is voided by the court, the parties can renegotiate a new agreement ex-post.  There are two effects of a court that voids more contracts. The parties' incentives to undertake relationship-specific investment are reduced, while the parties enjoy greater insurance against the unforeseen contingencies which the ex-ante contract cannot take into account.  In this context, we are able to characterize fully the optimal decision rule for the court. The behavior of the optimal court is determined by the tradeoff between the need for incentives and the gains from insurance that voiding in some circumstances offers to the agents. Download Paper
We construct a model in which the ambiguity of candidates allows them to increase the number of voters to whom they appeal when voters have intense preferences for one of the alternatives available. An ambiguous candidate may offer voters with different preferences the hope that their most preferred alternative will be implemented. We find conditions under which ambiguous strategies are chosen in equilibrium. These conditions include the case in which there is an outcome that is a majority winner against all other outcomes but is not the most preferred outcome for a majority of voters. It is shown that if the number of candidates or parties increases, ambiguity will not be possible in equilibrium, but a larger set of possible policies increases the chance that at least one candidate will choose to be ambiguous in equilibrium. Download Paper
This paper addresses the question of whether agents will invest efficiently in attributes that will increase their productivity in subsequent matches with other individuals. We present a two-sided matching model in which buyers and sellers make investment decisions prior to a matching stage. Once matched, the buyer and seller bargain over the transfer price. In contrast to most matching models, preferences over possible matches are affected by decisions taken before the matching process. We show that if bargaining respects the existence of outside options (in the sense that the resulting allocation is in the core of the assignment game), then efficient decisions can always be sustained in equilibrium. However, there may also be inefficient equilibria. Our analysis identifies a potential source of inefficiency not present in most matching models. Download Paper