A new necessary condition for implementation in iteratively undominated strategies

We uncover a new necessary condition for implementation in iteratively undominated strategies by mechanisms that satisfy the “best element property” where for each agent, there exists a strategy profile that gives him the highest payoff in the mechanism. This class includes finite and regular mechanisms. We conclude that either the quasilinearity-like assumptions of available sufficiency results cannot be completely dispensed with or some mechanisms that do not satisfy the best element property must be employed. We term the condition “restricted deception-proofness.” It requires that, in environments with identical preferences, the social choice function be immune to all deceptions, making it then stronger than incentive compatibility. In some environments the conditions for (exact or approximate) implementation by mechanisms satisfying the best element property are more restrictive than previously thought.     

Rationalizable implementation

We consider the implementation of social choice functions under complete information in rationalizable strategies. A strict version of the monotonicity condition introduced by Maskin is necessary under the solution concept of rationalizability. Assuming the social choice function is responsive, i.e. in distinct states it selects distinct outcomes, we show that strict Maskin monotonicity is also sufficient under a mild “no worst alternative” condition. In particular, no economic condition is required. We discuss how our results extend when the social choice function is not responsive.     

Agency conflicts in the presence of random private benefits from project implementation

We study a contracting problem where a principal delegates the decision to implement a “project” to an agent who obtains private information about the value of the project before making the implementation decision. Moral hazard arises because the agent gets private random non-contractible benefits, or incurs private random non-contractible costs, if the project is implemented. This contracting problem is pervasive, when “project” and “benefits” are interpreted broadly.     

Role of honesty in full implementation

This paper introduces a new concept of full implementation that takes into account agents’ preferences for understanding how the process concerning honest reporting works. We assume that the agents have intrinsic preferences for honesty in the sense that they dislike the idea of lying when it does not influence their welfare but instead goes against the intention of the central planner. We show that the presence of such preferences functions in eliminating unwanted equilibria from the practical perspective, even if the degree of the preference for honesty is small. The mechanisms designed are detail free and involve only small fines.     

The measurement of rank mobility

In this paper we investigate the problem of measuring social mobility when the social status of individuals is given by their rank. In order to sensibly represent the rank mobility of subgroups within a given society, we address the problem in terms of partial permutation matrices which include standard (“global”) matrices as a special case. We first provide a characterization of a partial ordering on partial matrices which, in the standard case of global matrices, coincides with the well-known “concordance” ordering. We then provide a characterization of an index of rank mobility based on partial matrices and show that, in the standard case of comparing global matrices, it is equivalent to Spearman's ρ index.     

The communication requirements of social choice rules and supporting budget sets

The paper examines the communication requirements of social choice rules when the (sincere) agents privately know their preferences. It shows that for a large class of choice rules, any minimally informative way to verify that a given alternative is in the choice rule is by verifying a “budget equilibrium”, i.e., that the alternative is optimal to each agent within a “budget set” given to him. Therefore, any communication mechanism realizing the choice rule must find a supporting budget equilibrium. We characterize the class of choice rules that have this property. Furthermore, for any rule from the class, we characterize the minimally informative messages (budget equilibria) verifying it. This characterization is used to identify the amount of communication needed to realize a choice rule, measured with the number of transmitted bits or real variables. Applications include efficiency in convex economies, exact or approximate surplus maximization in combinatorial auctions, the core in indivisible-good economies, and stable many-to-one matchings.     

Interdependent preferences and segregating equilibria

This paper shows that models where preferences of individuals depend not only on their allocations, but also on the well being of other persons, can produce both large and testable effects. We study the allocation of workers with heterogeneous productivities to firms. We show that even small deviations from purely “selfish” preferences leads to widespread workplace skill segregation. That is, workers of different abilities tend to work in different firms, as long as they care somewhat more about the utilities of workers who are “close”. This result holds for a broad class and distribution of social preferences.     

The structure of strategy-proof social choice — Part I: General characterization and possibility results on median spaces

We define a general notion of single-peaked preferences based on abstract betweenness relations. Special cases are the classical example of single-peaked preferences on a line, the separable preferences on the hypercube, the “multi-dimensionally single-peaked” preferences on the product of lines, but also the unrestricted preference domain. Generalizing and unifying the existing literature, we show that a social choice function is strategy-proof on a sufficiently rich domain of generalized single-peaked preferences if and only if it takes the form of voting by issues (“voting by committees”) satisfying a simple condition called the “Intersection Property.”Based on the Intersection Property, we show that the class of preference domains associated with “median spaces” gives rise to the strongest possibility results; in particular, we show that the existence of strategy-proof social choice rules that are non-dictatorial and neutral requires an underlying median space. A space is a median space if, for every triple of elements, there is a fourth element that is between each pair of the triple; numerous examples are given (some well-known, some novel), and the structure of median spaces and the associated preference domains is analysed.     

Can micro-credit bring development?

We examine the long-run effects of micro-credit on development in an occupational choice model similar to Banerjee and Newman (JPE, 1993). Micro-credit is modeled as a pure improvement in the credit market that opens up self-employment options to some agents who otherwise could only work for wages or subsist. Micro-credit can either raise or lower long-run GDP, since it can lower use of both subsistence and full-scale industrial technologies. It typically lowers long-run inequality and poverty, by making subsistence payoffs less widespread. Thus, an equity-efficiency tradeoff may be involved in the promotion of micro-credit. However, in a worst case scenario, micro-credit has purely negative long-run effects. The key to micro-credit's long-run effects is found to be the “graduation rate”, defined as the rate at which the self-employed build up enough wealth to start full-scale firms. We distinguish between two avenues for graduation: “winner” graduation (of those who earn above-average returns in self-employment) and “saver” graduation (due to gradual accumulation of average returns in self-employment). Long-run development is not attainable via micro-credit if “winner” graduation is the sole avenue for graduation. In contrast, if the saving rate and self-employment returns of the average micro-borrower are jointly high enough, then micro-credit can bring an economy from stagnation to full development through “saver” graduation. Thus the lasting effects of micro-credit may partially depend on simultaneous facilitation of micro-saving. Eventual graduation of the average borrower, rather than indefinite retention, should be the goal of micro-banks if micro-credit is to be a stepping stone to broad-based development rather than at best an anti-poverty tool.     

Innovation management in organizations

This paper poses the question of how a firm should optimally choose both its organization and its compensation in the pursuit of innovation. One key result is that incentive pay arises as a robust instrument of innovation management both with and without delegation, although in the present model its primary purpose is not to elicit more effort for the creation of new ideas, but to ensure that new ideas are implemented if and only if this is efficient. While without delegation, the firm may “underinvest” in innovation, with delegation the opposite bias may arise as new ideas may be implemented too often (“overinvestment”). The optimal organizational choice trades off these two biases.     

Voting over type and generosity of a pension system when some individuals are myopic

This paper studies the determination through majority voting of a pension scheme when society consists of far-sighted and myopic individuals. All individuals have the same basic preferences but myopics tend to adopt a short-term view (instant gratification) when dealing with retirement saving and labor supply. Consequently, they will find themselves with low consumption after retirement and regret their insufficient savings decisions. Henceforth, when voting they tend to commit themselves into forced saving. We consider a pension scheme that is characterized by two parameters: the payroll tax rate (that determines the size or generosity of the system) and the “Bismarckian factor” that determines its redistributiveness. Individuals vote sequentially. We examine how the introduction of myopic agents affects the generosity and the redistributiveness of the pension system. Our main result is that a flat pension system is always chosen when all individuals are of one kind (all far-sighted or all myopic), while a less redistributive system may be chosen if society is composed of both myopic and far-sighted agents. Furthermore, while myopic individuals tend to prefer larger payroll taxes than their far-sighted counterparts, the generosity of the system does not always increase with the proportion of myopics.     

Voluntary formation of communities for the provision of public projects

In this paper we examine a group formation problem, where heterogeneous individuals partitioned themselves into communities, each choosing its own public project from the given space of feasible projects. The model is that of “horizontal product differentiation” where individuals display distinct preferences over the policy space. We consider the notion of “efficient” configuration that minimizes the total project-related costs and aggregate personalized costs of all individuals, and “sustainable” configurations, those are immune against breakaways by subgroups of individuals. Our main result is that, with a unidimensional project space and single-peaked personalized costs, every efficient partition is sustainable.     

Designing social security - a portfolio choice approach

Public social security systems may provide diversification of risks to individuals’ life-time income. Capturing that a pay-as-you-go system (paygo) may be considered as a “quasi-asset”, we study the optimal size of the paygo system as well as the optimal split between funded and unfunded pension saving by means of a theoretical portfolio choice framework. A low-yielding paygo system can benefit individuals if it contributes to hedge other risks to their lifetime resources. Numerical calculations indicate that optimal social security systems should be at least partly paygo financed in many economies. The optimal magnitude of the paygo system depends on the specified risk concept as well as the stochastic properties of stock market returns and implicit paygo-returns.     

Collective management of residential housing in Russia: The importance of being social

Homeowners associations (HOAs) implement collective management in residential housing. We assess the performance of such associations in Russia by using the stochastic frontier technique. Cultural traits enabling tenants to make proper use of the HOA decision-making procedures are essential for resolving the collective action problem and ensure accountability of governing bodies and outside contractors. Such “technical civic competence” has a stronger impact on HOA performance than more conventional forms of social capital which rise in their significance when HOA governance breaks down and informal grassroots alternatives are mobilized instead. Massive and indiscriminate “supply-led” introduction of collective management in residential housing without matching cultural and institutional prerequisites could be counterproductive. Flexibility, freedom of choice, and market development are required to avert the failures of HOAs commonly observed in Russia.     

Arrovian aggregation in economic environments: how much should we know about indifference surfaces?

Arrow's celebrated theorem of social choice shows that the aggregation of individual preferences into a social ordering cannot make the ranking of any pair of alternatives depend only on individual preferences over that pair, unless the fundamental weak Pareto and non-dictatorship principles are violated. In the standard model of division of commodities, we investigate how much information about indifference surfaces is needed to construct social ordering functions satisfying the weak Pareto principle and anonymity. We show that local information such as marginal rates of substitution or the shapes “within the Edgeworth box” is not enough, and knowledge of substantially non-local information is necessary.     

A characterization of consistent collective choice rules

We characterize a class of collective choice rules such that collective preference relations are consistent. Consistency is a weakening of transitivity and a strengthening of acyclicity requiring that there be no cycles with at least one strict preference, which excludes the possibility of a “money pump.” The properties of collective choice rules used in our characterization are unrestricted domain, strong Pareto, anonymity and neutrality. If there are at most as many individuals as there are alternatives, the axioms provide an alternative characterization of the Pareto rule. If there are more individuals than alternatives, however, further rules become available.     

Misery loves company: Social regret and social interaction effects in choices under risk and uncertainty

Extensive field evidence shows individuals? decisions in settings involving uncertainty depend on their peers? decisions. One hypothesized cause of peer group effects is social interaction effects: an individual?s utility from an action is enhanced by others taking the same action. We employ a series of controlled laboratory experiments to study the causes of peer effects in choice under uncertainty. We find strong peer group effects in the laboratory. Our design allows us to rule out social learning, social norms, group affiliation, and complementarities as possible causes for the observed peer group effects, leaving social interaction effects as the likely cause. We use a combination of theory and empirical analysis to show that preferences including “social regret” are more consistent with the data than preferences including a taste for conformity. We observe spillover effects, as observing another?s choice of one risky gamble makes all risky gambles more likely to be chosen.     

Are incentives against economic justice?

We consider the problem of fairly allocating a social endowment of indivisible goods and money when the domain of admissible preferences contains, but is not restricted to, quasi-linear preferences. We analyze the manipulability of the Generalized Money Rawlsian Fair (GMRF) solutions. (i) We show that the Nash and strong Nash equilibrium correspondences of the “preference revelation game form” associated with each GMRF solution coincide with the no-envy solution (in equilibrium, efficiency is preserved according to agents' true preferences). (ii) A corollary is that the GMRF solutions “naturally implement” the no-envy solution in Nash and strong Nash equilibria.     

Judgment aggregation: (im)possibility theorems

The aggregation of individual judgments over interrelated propositions is a newly arising field of social choice theory. I introduce several independence conditions on judgment aggregation rules, each of which protects against a specific type of manipulation by agenda setters or voters. I derive impossibility theorems whereby these independence conditions are incompatible with certain minimal requirements. Unlike earlier impossibility results, the main result here holds for any (non-trivial) agenda. However, independence conditions arguably undermine the logical structure of judgment aggregation. I therefore suggest restricting independence to “premises”, which leads to a generalised premise-based procedure. This procedure is proven to be possible if the premises are logically independent.     

On the size and structure of group cooperation

When time preferences are heterogeneous and bounded away from one, how “much” cooperation can be achieved by an ongoing group? How does group cooperation vary with the group's size and structure? This paper examines characteristics of cooperative behavior in the class of symmetric, repeated games of collective action. These are games characterized by “free rider problems” in the level of cooperation achieved. The Repeated Prisoner's Dilemma games is a special case.We characterize the level of maximal average cooperation (MAC), the highest average level of cooperation, over all stationary subgame perfect equilibrium paths, that the group can achieve. The MAC is shown to be increasing in monotone shifts, and decreasing in mean preserving spreads of the distribution of discount factors. The latter suggests that more heterogeneous groups are less cooperative on average. Finally, in a class of Prisoner's Dilemma games, we show under weak conditions that the MAC exhibits increasing returns to scale in a range of heterogeneous discount factors. That is, larger groups are more cooperative, on average, than smaller ones. By contrast, when the group has a common discount factor, the MAC is invariant to group size.