In most industries, ranging from information systems development to construction, an overwhelming proportion of projects are delayed beyond estimated completion time. This fact constitutes somewhat of a puzzle for existing theory. The present paper studies project delays and optimal contracts under moral hazard in a setting with time to build. Within this setup, project delays are found to be most likelyto happen at early stages of development, and intimately connected to the degree ofcommitment of the procurer and the class of contracts that can be enforced. The firstbest,optimal spot contracting and optimal long-term contract scenarios are analyzed, aswell as commonly encountered additional constraints on the long-term contract.

It is commonly accepted that face-to-face communication induces cooperation. The experiment disentangles communication and social effect (replication of Roth, 1995) and examines the components of the social effect with the help of unilateral communication. Results suggest that separate processes, both of a strategic and of an affective-social nature may induce cooperative outcomes in ultimatum bargaining with pre-play communication, depending on the communication protocol. Unilateral communication is found to have weaker effects than bilateral communication, and affects especially the recipient of the communication.

Three values for non-transferable utility games – the Harsanyi NTU-value, the Shapley NTU-value, and the Maschler-Owen consistent NTU-value – are compared in a simple example.

The Maschler-Owen consistent value for non-transferable utility games is axiomatized, by means of a marginality axiom.

Behavior in dynamic competitive situations requires decision makers to evaluate their own as well as their competitors positions. This paper uses data from a realistic competitive risk taking setting, Jeopardy s Tournament of Champions, to test whether individual players choose the strategic best response in making their betting decisions. The analyses show that the percentage of players choosing the strategic best response is very low, a rather surprising finding because the Tournament of Champions is contested by the very best and most experienced players of the Jeopardy game. We conjecture that performance aspiration and survival targets guide risk-taking behavior in competitive situations. Furthermore, in situations where decisions are made under pressure, contestants tend to focus on one target while ignoring alternative targets and the choices that are available to their competitors. This may lead them to select inferior competitive strategies.

The asymptotic value, introduced by Kannai in 1966, is an asymptotic approach to the notion of the Shapley value for games with infinitely many players. A vector measure game is a game v where the worth v(S) of a coalition S is a function f of ¼(S) where ¼ is a vector measure. Special classes of vector measure games are the weighted majority games and the two-house weighted majority games where a two-house weighted majority game is a game in which a coalition is winning if and only if it is winning in two given weighted majority games. All weighted majority games have an asymptotic value. However, not all two-house weighted majority games have an asymptotic value. In this paper we prove that the existence of infinitely many atoms with sufficient variety suffice for the existence of the asymptotic value in a general class of nonsmooth vector measure games that includes in particular two-house weighted majority games.

Gradual bargaining is represented by an agenda: a family of increasing sets of joint utilities, parameterized by time. A solution for gradual bargaining specifies an agreement at each time. We axiomatize an ordinal solution, i.e., one that is covariant with order-preserving transformations of utility. It can be viewed as the limit of a step-by-step bargaining in which the agreement of the last negotiation becomes the disagreement point for the next. The stepwise agreements may follow the Nash solution, the Kalai-Smorodinsky solution or many others.

When individuals choose from whatever alternatives available to them the one that maximizes their utility then it is always desirable that the government provide them with as many alternatives as possible. Individuals, however, do not always choose what is best for them and their mistakes may be exacerbated by the availability of options. We analyze self-selection models, when individuals know more about themselves than it is possible for governments to know, and show that it may be socially optimal to limit and sometimes to eliminate individual choice. As an example, we apply Luce s (1959) model of random choice to a work-retirement decision model and show that the optimal provision of choice is positively related to the degree of heterogeneity in the population and that even with very small degrees of non-rationality it may be optimal not to provide individuals any choice.

When the amount of information to be dealt with exceeds people s short-term memory capacity, they must resort to the sampling of information. In the present study we show that, under conditions of cognitive overload (which could result from decision-making under stress, time constraints or information abundance), individuals exhibit systematic differences in estimating variance. Moreover, these differences critically depend on the format of the evidence presented: Variance is downward attenuated when information is presented analogically, but amplified when it is presented numerically. These distortions in the perception of variance affect individuals pricing of risky alternatives. We suggest that these results may help to explain economic anomalies, such as excess trading in financial markets. We also point out possibilities for manipulating the perception of variability and normative implications concerning the presentation of information on the variance of phenomena.

We present three axioms for a power index defined on the domain of simple (voting) games. Positivity requires that no voter has negative power, and at least one has positive power. Transfer requires that, when winning coalitions are enhanced in a game, the change in voting power depends only on the change in the game, i.e., on the set of new winning coalitions. The most crucial axiom is composition: the value of a player in a compound voting game is the product of his power in the relevant first-tier game and the power of his delegate in the second-tier game. We prove that these three axioms categorically determine the Banzhaf index.

Voting problems with a continuum of voters and finitely many alternatives are considered. The classical Arrow and Gibbard-Satterthwaite theorems are shown to persist in this model, not for single voters but for coalitions of positive size. The emphasis of the study is on strategic considerations, relaxing the nonmanipulability requirement: are there social choice functions such that for every profile of preferences there exists a strong Nash equilibrium resulting in the alternative assigned by the social choice function? Such social choice functions are called exactly and strongly consistent. The study offers an extension of the work of Peleg (1978a) and others. Specifically, a class of anonymous social choice functions with the required property is characterized through blocking coefficients of alternatives, and associated effectivity functions are studied. Finally, representation of effectivity functions by game forms having a strong Nash Equilibrium is studied.

A game form constitutionally implements a social choice correspondence if it implements it in Nash equilibrium and, moreover, the associated effectivity functions coincide. This paper presents necessary and sufficient conditions for a unanimous social choice correspondence to be constitutionally implementable, and sufficient and almost necessary conditions for an arbitrary (but surjective) social choice correspondence to be constitutionally implementable. It is shown that the results apply to interesting classes of scoring and veto rules.

We address the issue of the representation as well as the evolution of (possibly) mistaken beliefs. We develop a formal setup (a mutual belief space) in which agents might have a mistaken view of what the model is. We then model a communication process, by which agents communicate their beliefs to one another. We define a revision rule that can be applied even when agents have contradictory beliefs. We study its properties and, in particular, show that, when mistaken, agents do not necessarily eventually agree after communicating their beliefs. We finally address the dynamics of revision and show that when beliefs are mistaken, the order of communication may affect the resulting belief structure.

We prove a difference equation analogue for the decay-of-mass result for the nonlinear parabolic equation ut = ”u + ¼ |ˆ‡u| when ¼ 0.

We analyse a common value, alternating ascending bid, first price auction as a repeated game of incomplete information where the bidders hold equal property rights to the object auctioned off. Consequently they can accept (by quitting) or veto any proposed settlement. We characterise the essentially unique, sequentially rational dynamic Bayesian Nash equilibrium of this game under incomplete information on one side and discuss its properties.

A Nobel Prize in Economics was given to the psychologist Daniel Kahneman for his joint research with the late psychologist Amos Tversky on decision making under uncertainty and on subjective judgments of uncertainty. The two proposed Prospect Theory as a descriptive alternative to Utility Theory, the reigning normative theory of choice under uncertainty. Kahneman and Tversky argued that human psychology prevents people from being rational in the sense required by Utility Theory – consistency – for two main reasons. First, people are more sensitive to changes in position (economic or otherwise) than to final positions, a fact ignored by Utility Theory. Thus, they value a 50% discount on a 100NIS item more than a 5% discount on a 1000 NIS item. Moreover, they are more sensitive to changes for the worse than to changes for the better. Second, we are sensitive not just to outcomes, but to outcomes-under-a-description, which makes us inconsistent from a consequentialist veiwpoint (e.g., we don't feel the same about losing 100 NIS on our way to the theater boxoffice, vs. losing a 100 NIS ticket on our way to the theater). The article describes some of the empirical observations that led to the development of Prospect Theory, and some of its basic tenets.

Models have been put forward recently that seem to be successful in explaining apparently anomalous experimental results in the Ultimatum Game, where responders reject positive offers. While imparting fixed preference orders to fully rational agents, these models depart from traditional models by assuming preferences that take account not only of the material payoff to oneself, but also of that which is given to others. However, they leave open the question of how an agent's economic survival is helped by a preference order that advises him to leave money on the table. Our answer is that, indeed, doing so does not help. But that the same envious preference order that ill advises in some circumstances to reject an "insultingly" small offer, advises well in other circumstances, when it helps the same agent to overcome his risk- aversion and to offer a risky, tough offer that yields him a higher expected dollar gain. We show the existence of population distributions where the two effects exactly balance out across different preference types. These distributions are stable, stationary, and inefficient, in which different preferences asymptotically are represented, and where, as commonly observed in an Ultimatum Game, positive offers are made, of which some are rejected with positive probability. Our theory yields new testable hypotheses.

We propose two sequential mechanisms for efficient production of public goods. Our analysis differs from the existing literature in allowing for the presence of multiple public goods and in also being simple.  While both mechanisms ensure efficiency, the payoffs in the first mechanism are asymmetric, being sensitive to the order in which agents move. The second mechanism corrects for this through a two-stage game where the order of moves in the second stage are randomly determined. The payoffs from the second mechanism correspond to the Shapley value of a well-defined game which summarizes the production opportunities available to coalitions in the economy.

Animal conflicts are often characterized by time dependent strategy sets. This paper considers the following type of animal conflicts: a member of a group is at risk and needs the assistance of another member to be saved. As long as assistance is not provided, the individual which is at risk has a positive, time dependent rate of dying. Each of the other group members is a potential helper. Assisting this individual accrues a cost, but losing him decreases the inclusive fitness of each group member. A potential helper s interval between the moment an individual finds itself at risk and the moment it assists is a random variable, hence its strategy is to choose the probability distribution for this random variable. Assuming that each of the potential helpers knows the others strategies, we show that the ability to observe their realizations influences the Evolutionarily Stable Strategies (ESS) of the game. According to our results, where the realizations can be observed ESS always exist: immediate assistance, no assistance and delayed assistance. Where the realizations cannot be observed ESS do not always exist, immediate assistance and no assistance are possible ESS, while delayed assistance cannot be an ESS. We apply our model to the n brothers problem and to the parental investment conflict.