从事前效率问题到事后效率问题——不完全合同理论的几类经典模型比较

通过对不完全合同经典理论模型的组成要素的梳理和分类,本文首次将不完全合同理论的模型分为四种类型:行动事前不可缔约而事后可缔约的事前效率问题模型,行动事前和事后都不可缔约的事前和事后效率问题模型,事前部分可缔约的事前和事后效率问题模型,收益事后不可证实的事前和事后效率问题模型。这些不同的理论被纳入一个统一的框架中进行表述。传统的产权理论具有一些缺陷,而事后不可缔约的模型更适合研究权威、授权、科层等问题。相对于关于投资激励的事前效率问题,事后效率问题的来源要多得多。对事前与事后缔约性问题的探讨以及对事后效率问题的研究是丰富不完全合同理论发展的动力。     

EX POST VERSUS EX ANTE MEASURES OF THE USER COST OF CAPITAL

Should we use ex post or ex ante measures of user costs to calculate the contribution of capital in a growth accounting exercise? The answer, based on a simple model of temporary equilibrium, is that ex post is better in theory. In practice researchers usually calculate ex post user costs by assuming that the rate of return is equalized across assets. But this is only true if expectations are correct. In general, the ex post rate of return differs between assets, even though ex ante it is the same. I propose a hybrid method. The index of capital services is estimated using ex ante weights; the contribution of capital is the growth of this index multiplied by the ex post income share of capital. I show that this method is theoretically correct if the production function is CES. I compare the ex post, ex ante and hybrid methods using data for 31 U.K. industries from 1970 to 2000.     

Ex post implementation

We analyze the problem of fully implementing a social choice set in ex post equilibrium. We identify an ex post monotonicity condition that is necessary and—in economic environments—sufficient for full implementation in ex post equilibrium. We also identify an ex post monotonicity no veto condition that is sufficient. Ex post monotonicity is satisfied in all single crossing environments with strict ex post incentive constraints.We show by means of two classic examples that ex post monotonicity does not imply nor is it implied by Maskin monotonicity. The single unit auction with interdependent valuations is shown to satisfy ex post monotonicity but not Maskin monotonicity. We further describe a Pareto correspondence that fails ex post monotonicity but satisfies Maskin monotonicity.     

On competitive balance in the group stage of the UEFA Champions League*

This article examines competitive balance in the group stage of the UEFA Champions League over the last two decades (1999/2000–2017/2018). Competitive balance is considered both before and after a competition. Have the groups been designed in such a way as to ensure similar levels of competitive balance ex ante? Have the demonstrated strengths (ex post competitive balance) of the different groups been similar over each season? What is the relationship between the competitive balance in the designed groups and that achieved in the same groups after the competition? Are the performance achieved in terms of ex post competitive balance similar to ex ante competitive balance levels? We found that, despite expectations, the groups' ex ante competitive balance was not homogeneous. Although ex ante competitive balance serves as a good predictor, on average, of ex post competitive balance, we observed significant differences at the levels of group and seasons. Therefore, it is possible to improve the design mechanism of the groups that make up the group stage of the champions so that they are composed homogeneously in terms of ex ante competitive balance.     

Unequal uncertainties and uncertain inequalities: an axiomatic approach

In this paper, we provide an axiomatic characterization of social welfare functions for uncertain incomes. Our most general result is that a small number of reasonable assumptions regarding welfare orderings under uncertainty rule out pure ex ante as well as pure ex post evaluations. Any social welfare function that satisfies these axioms should lie strictly between the ex ante and the ex post evaluations of income distributions. We also provide an axiomatic characterization of the weighted average of the minimum and the maximum of ex post and ex ante evaluations.     

Location decisions of a polluting firm and the time consistency of environmental policy

This paper considers location decisions of a monopolist, who faces a tax on its emissions in the home country, under ex post that is, time consistent, and ex ante, that is precommitment, environmental policies. We show that the monopolist will relocate more often under ex post optimal emission taxes. A government which cannot commit to an ex ante emission tax and sets its tax ex post after abatement effort has been chosen, is unable to affect the monopolist’s location decision, because it cannot commit to strategically reduce its tax level in the first stage. Domestic welfare is often higher under ex post emission taxes whenever the monopolist relocates under both policy regimes. Otherwise, welfare is higher under government commitment to an ex ante emission tax level. Thus, government commitment to a policy is not always welfare improving.     

The role of ex ante and ex post decisions in the valuation of life

This paper examines the use of ex ante and ex post criteria in the evaluation of projects involving the risk of death. One issue concerns the appropriate welfare function, and it is argued that this should reflect both ex post and ex ante considerations, but not in the form of restrictions on the welfare function. The second issue concerns the form of compensation. The argument in favour of ex post compensation as a means of reducing the cost of risk-bearing needs to be modified when risks involve more than a single dimension as they do in projects involving the risk of death.     

Complexity and Renegotiation: A Foundation for Incomplete Contracts

The paper considers a hold-up model where only one of n future trading opportunities will prove to be efficient, and where ex post renegotiation of the ex ante contract cannot be prevented. As the environment becomes more complex ( n →∞), the outcome under any message-contingent long-term contract converges to that of the "incomplete contracting" model where trade is contractible ex post , but not ex ante . When trades are costly to describe, both ex ante and ex post , the incomplete contracting result is extended to a broader class of environments.     

Ordinary Shares and Managers

We argue that ordinary shares undermine any inherent commitment of its holders to resist renegotiating away ex post inefficiencies. Yet, in a dynamic adverse selection problem, such ex post inefficiencies are optimal from an ex ante point of view. We show that shareholders may use a manager in combination with a golden parachute (managerial severance payments) as a commitment device not to renegotiate ex post.     

Discrepancies between ex ante and ex post efficiency under identical subjective probabilities

Summary. Starr (1973) showed that, if people have different subjective probabilities, ex ante and ex post efficiency conflict. Conversely, under the simple preferences that he considered, the discrepancy between ex ante and ex post efficiency disappears when subjective probabilities are identical. Here I consider identical subjective probabilities, but more general preferences. First, risk attraction is admitted. Second, I dispense with the double requirement (dubbed IZU) of additive separability and state-independence of the utility of zero-date consumption, an unrealistic requirement when modeling the investment in durable goods. I find that, under IZU, and as long as ex post preferences satisfy the natural assumption of quasiconcavity (and satisfy some technical qualifications), an ex ante efficient allocation is indeed ex post efficient, but the converse is not necessarily true under risk attraction. If, on the other hand, IZU is violated, then one can have ex ante efficient allocations that are not ex post efficient, and vice-versa, even under risk aversion. Received: June 25, 1999; revised version: March 2001     

The theory of capital utilization and the putty-rubber production function

This paper extends the theory of optimal shift-work to the presumably realistic case in which the ex post elasticity of substitution between labor and capital services is neither zero nor equal to the ex ante elasticity. The paper considers both the CES and the VES as candidates for the ex post function, and gives reasons for preferring the latter. The introduction of ex post substitutability where none existed before is found to increase the profitability of shift-work.     

The public management of risk: Separating ex ante and ex post monitors

When a firm undertakes risky activities, the conflict between social and private incentives to implement safety care requires public intervention which can take the form of both monetary incentives and also ex ante or ex post monitoring, i.e., before or after an accident occurs. We delineate the optimal scope of monitoring depending on whether public monitors are benevolent or corruptible. We show that separating the ex ante and the ex post monitors increases the likelihood of ex post investigation, helps prevent capture and improves welfare.     

Hybrid Contests

This paper examines hybrid contests where participants commit two types of resources to improve their probability of winning the prize. The first type is forfeited ex ante, before the prize is allocated, by winners and losers alike, while the second is committed ex ante by all contenders but expended ex post, after the prize is allocated, and only by the contestant that wins the prize. The model yields a number of interesting results. Among them is the finding that, as the number of contestants increases, the ex ante expenditures of individual contestants decrease while the ex post expenditure increases. Even more interesting, the total of the ex ante and ex post expenditures by the contenders in a hybrid contest may decrease with the number of competitors. The study also finds that there is no rent overdissipation, and compares the total expenditures in the contest and “all‐pay” allocation mechanisms.     

Increasing consumer well-being: risk as potential driver of happiness

This article investigates the relation between risk and individual well-being. We propose a theoretical model of happiness that makes a distinction between ex ante evaluations of happiness and ex post assessments. The main assumptions of the model are tested through three studies based on anchoring vignettes. We show that, even if, ex ante, consumers fear high risk and do not associate it to a high level of happiness, their ex post evaluation of well-being is generally higher when identical consequences result from a high-risk situation than from a low-risk situation. Control over risk-taking reinforces the gap between ex ante and ex post measures of happiness. Thus, our article provides empirical evidence about a positive relation between risk and individual well-being, suggesting that risky experiences have the potential to increase consumer well-being.     

Bargaining In International Trade Under Exchange-Rate Uncertainty

This paper examines the implications of various contracting alternatives between exporting and importing firms on the volume of international transactions. the contracts that we study are determined in a bargaining situation under exchange-rate uncertainty. First we look at contracts which entail an ex ante commitment on price and quantity of exports without the possibility of renegotiation ex post. Second, spot contracts, i.e., the price and the quantity of exports are negotiated after the exchange the rate is known. A third type of contracts consists of ex ante commitment and ex post renegotiation.     

Experiments on unemployment benefit sanctions and job search behavior

This paper presents the results of an experimental study on unemployment benefit sanctions. The experimental set-up allows us to distinguish between the effect of benefit sanctions once they are imposed (the ex post effect) and the threat of getting a benefit sanction imposed (the ex ante effect). We find that both effects matter. Moreover, the ex ante effect turns out to be substantial and bigger than the ex post effect. Benefits sanctions stimulate the outflow from unemployment.     

Vertical integration and transaction-specific sunk costs

The purpose of this paper is to analyze vertical integration, long-term contracts and spot markets as institutional alternatives when transaction-specific investments are involved. Firm activities are divided into two periods. In the first period (the ex ante world), decisions on the amount of transaction-specific sunk costs are made, whereas after realization of a random state of the world, short-run production decisions are made (in the ex post world). The problem analyzed is to determine what form of organizations and/or contracts will emerge between upstream and downstream firms in the ex ante world to regulate their ex ante transaction-specific investments, if any, as well as their ex post production decisions and the distribution of resulting profits.     

On efficient partnership dissolution under ex post individual rationality

This paper studies ex post individually rational, efficient partnership dissolution in a setting with interdependent valuations. We derive a sufficient condition that ensures the existence of an efficient dissolution mechanism that satisfies Bayesian incentive compatibility, ex post budget balancedness, and ex post individual rationality. For equal-share partnerships, we show that our sufficient condition is satisfied for any symmetric type distribution whenever the interdependence in valuations is non-positive. This result improves former existence results, demonstrating that the stronger requirement of ex post individual rationality does not always rule out efficiency. We also show that if we allow for two-stage revelation mechanisms, in which agents report their realized payoffs from the allocation, as well as imposing penalties off the equilibrium path, efficient dissolution is always possible even when the interdependence is positive. We further discuss the possibility of efficient dissolution with ex post quitting rights.     

On the efficiency of ex ante and ex post pricing institutions

Summary This paper compares the performance of three pricing institutions in a decentralized matching model in which random matching occurs. In the first, sellers make public ex ante commitments to trade at pre-specified prices before matching occurs. In the second, the buyer and seller engage in an alternating offer bargaining game once a match has occurred. In the final pricing institution, one party is chosen at random to make a take it or leave it price offer. The steady state equilibrium with ex ante pricing pareto dominates the steady state equilibrium with ex post take it or leave it offers, which in turn pareto dominates the steady state equilibrium with alternating offers. As the discount factor goes to one, the equilibrium with ex ante pricing generates participation rates that tend toward the pareto efficient level. The ex post pricing institutions generate participation rates that are bounded away from efficient levels. The surplus loss associated with switching from ex ante pricing to take it or leave it offers is small when the discount factor is close to one. Contrary to many models of decentralized trade, ex post pricing institutions encourage too much search by buyers.The financial support of the Social Sciences and Humanities Research Council of Canada is gratefully acknowledged. The research for this paper was completed while the author was visiting the University of California at San Diego. The author thanks Douglas Gale for comments.