Weak covering relations

This paper proposes and justifies a natural way to weaken the concept of covering relation defined on a finite tournament. Various weak covering relations, calledk-covering relations, are introduced. To eachk-covering relation corresponds a strong uncovered set containing all nonk-covered outcomes. It is proved that those strong uncovered sets may be empty. Moreover, the set of all tournaments having an empty strong uncovered set is characterized within two rather large classes of tournaments. Finally, we offer a complete study of the cases where the directed graph defined by ak-covering relation coincides with the initial tournament.     

Ranking sets additively in decisional contexts: an axiomatic characterization

Ranking finite subsets of a given set X of elements is the formal object of analysis in this article. This problem has found a wide range of economic interpretations in the literature. The focus of the article is on the family of rankings that are additively representable. Existing characterizations are too complex and hard to grasp in decisional contexts. Furthermore, Fishburn (1996), Journal of Mathematical Psychology 40, 64–77 showed that the number of sufficient and necessary conditions that are needed to characterize such a family has no upper bound as the cardinality of X increases. In turn, this article proposes a way to overcome these difficulties and allows for the characterization of a meaningful (sub)family of additively representable rankings of sets by means of a few simple axioms. Pattanaik and Xu’s (1990), Recherches Economiques de Louvain 56, 383–390) characterization of the cardinality-based rule will be derived from our main result, and other new rules that stem from our general proposal are discussed and characterized in even simpler terms. In particular, we analyze restricted-cardinality based rules, where the set of “focal” elements is not given ex-ante; but brought out by the axioms.      

Dynamic focal points in N-person coordination games

To understand how groups coordinate, we study infinitely repeated N-player coordination games in the context of strategic uncertainty. In a situation where players share no common language or culture, ambiguity is always present. However, finding an adequate principle for a common language is not easy: a tradeoff between simplicity and efficiency has to be made. All these points are illustrated on repeated N-player coordination games on m loci. In particular, we demonstrate how a common principle can accelerate coordination. We present very simple rules that are optimal in the space of all languages for m (number of coordination loci) from 2 to 5 and for all N, the number of players. We also show that when more memory is used in the language (strategies), players may not coordinate, whereas this is never the case when players remember only the previous period.     

On the coase theorem and coalitional stability: the principle of equal relative concession

The Coase theorem is argued to be incompatible with bargaining set stability due to a tension between the grand coalition and sub-coalitions. We provide a counter-intuitive argument to demonstrate that the Coase theorem may be in complete consonance with bargaining set stability. We establish that an uncertainty concerning the formation of sub-coalitions will explain such compatibility: each agent fears that others may `gang up' against him and this fear forces the agents to negotiate. The grand coalition emerges from the negotiations if each agent uses the principle of equal relative sacrifice to determine the actual allocation. We also establish the rational basis for the choice of the principle of equal relative concession by the negotiating agents. Hence we argue that the Coase theorem will be valid even if there are stable sub-coalitions.     

The general relevance of the impossibility teorem in smooth social choice

A complete classification theorem for voting processes on a smooth choice spaceW of dimensionw is presented. Any voting process is classified by two integersv ^* () andw(), in terms of the existence or otherwise of the optima set, IO(), and the cycle set IC().In dimension belowv ^* () the cycle set is always empty, and in dimension abovew() the optima set is nearly always empty while the cycle set is open dense and path con nected. In the latter case agenda manipulation results in any outcome.For admissible (compact, convex) choice spaces, the two sets are related by the general equilibrium result that IO() union IC() is non-empty. This in turn implies existence of optima in low dimensions. The equilibrium theorem is used to examine voting games with an infinite electorate, and the nature ofstructure induced equilibria, induced by jurisdictional restrictions.This material is based on work supported by a Nuffield Foundation grant.     

The BDNF gene val66met polymorphism and behavioral inhibition in early childhood

Stably elevated behavioral inhibition (BI) is an established risk factor for internalizing disorders. This stability may be related to genetic factors, including a valine‐to‐methionine substitution on codon 66 (val66met ) of the brain‐derived neurotrophic factor (BDNF) gene. Past work on the BDNF met variant has inconsistently linked it to vulnerability to internalizing problems; some of this inconsistency may stem from the failure to consider gene‐trait interactions in shaping the course of early BI. Toward elucidating early pathways to anxiety vulnerability, we examined gene‐by‐trait interactions in predicting the course of BI over time in 476 children, assessed for BI using standardized laboratory methods. We found that children with the met allele showed lower stability of BI between ages 3 and 6 than those without this allele. While the mechanisms that underlie this effect are unclear, our findings are consistent with the notion that the met variant, in the context of early BI, influences the stability of this trait in early development.     

Comparative accuracy of value solutions in non-sidepayment games with empty core

This article reports a test of the predictive accuracy of solution concepts in cooperative non-sidepayment n-person games with empty core. Six solutions were tested. Three of these were value solutions (i.e., -transfer value, -transfer nucleolus, and -transfer disruption value) and three were equilibrium solutions (deterrence set, stable set, and imputation set). The test was based on a laboratory experiment utilizing 5-person, 2-choice normal form games with empty core; other related data sets were also analyzed. Goodness-of-fit results based on discrepancy scores show that the three value solutions are about equally accurate in predicting outcomes, and that all three are substantially more accurate than the other solutions tested.     

An axiomatic analysis of the Nash equilibrium concept

The purpose of this paper is to analyze axiomatically the Nash equilibrium concept. The class of games under study is a (relatively large) subclass of n-person normal form games. Solutions are correspondences which associate to each game a non empty set of strategy vectors of this game. It is shown that if a solution satisfies the axioms Independence of irrelevant alternatives (IIA) and Individual rationality (IR), then all the strategy vectors in this solution are Nash equilibria. This result holds good also if IR is replaced by Strong individual monotonicity (SIM) or Weak principle of fair compromise (WPFC).     

Cooperative provision of indivisible public goods

A community faces the obligation of providing an indivisible public good that each of its members is able to provide at a certain cost. The solution is to rely on the member who can provide the public good at the lowest cost, with a due compensation from the other members. This problem has been studied in a non-cooperative setting by Kleindorfer and Sertel (J Econ Theory 64:20–34, 1994). They propose an auction mechanism that results in an interval of possible individual contributions whose lower bound is the equal division. Here, instead we take a cooperative stand point by modelling this problem as a cost sharing game that turns out to be a ‘reverse’ airport game whose core is shown to have a regular structure. This enables an easy calculation of the nucleolus that happens to define the upper bound of the Kleindorfer–Sertel interval. The Shapley value instead is not an appropriate solution in this context because it may imply compensations to non-providers.     

Not so cheap talk: costly and discrete communication

We model an interaction between an informed sender and an uninformed receiver. As in the classic cheap talk setup, the informed player sends a message to an uninformed receiver who is to take an action which affects the payoffs of both players. However, in our model, the sender can communicate only through the use of discrete messages which are ordered by the cost incurred by the sender. We characterize the resulting equilibria without refining out-of-equilibrium beliefs. Subsequently, we apply an adapted version of the no incentive to separate (NITS) condition to our model. We show that if the sender and receiver have aligned preferences regarding the action of the receiver, then NITS only admits the equilibrium with the largest possible number of induced actions. When the preferences between players are not aligned, we show that NITS does not guarantee uniqueness, and we provide an example where an increase in communication costs can improve communication. As we show, this improvement can occur to such an extent that the equilibrium outperforms the Goltsman et al. (J Econ Theory 144:1397–1420, 2009) upper bound for receiver’s payoffs in mediated communication.     

Assessing the Effects of an Asset-Building Program in Resource-Constrained Households: The Case of Sub-Saharan Africa

ABSTRACT

Using a survey that was administered individually to respondents at set locations, this study examines the effects of participation in an asset-building program in resource-constrained households in rural Ghana (n = 120 in the experimental group and n = 120 in the comparison group). Results suggest the program is effective in reaching the most economically vulnerable households. We also learned that program participation was related to ownership of social assets, as well as psychosocial and financial well-being. Program characteristics, including trust among members and time spent on program-related activities, were related to enhanced social and financial assets, respectively. A number of implications emerge from this study. Given that the program, although effective in reaching the most economically vulnerable households, did not produce significant outcomes in such households, attention may be devoted to understanding ways to enhance the welfare of vulnerable program participants. A targeted approach may be a viable option. With respect to policy, consideration could be given to incorporating microfinance models in poverty alleviation strategies. Continued research using more rigorous design is needed to explore the relationship between microfinance and the welfare of vulnerable participants.     

Even-chance lotteries in social choice theory

This paper discusses aspects of the theory of social choice when a nonempty choice set is to be determined for each situation, which consists of a feasible set of alternatives and a preference order for each voter on the set of nonempty subsets of alternatives. The individual preference assumptions include ordering properties and averaging conditions, the latter of which are motivated by the interpretation that subset A is preferred to subset B if and only if the individual prefers an even-chance lottery over the basic alternatives in A to an even-chance lottery over the basic alternatives in B. Corresponding to this interpretation, a choice set with two or more alternatives is resolved by an even-chance lottery over these alternatives. Thus, from the traditional no-lottery social choice theory viewpoint, ties are resolved by even-chance lotteries on the tied alternatives. Compared to the approach which allows all lotteries to compete along with the basic alternatives, the present approach is a contraction which allows only even-chance lotteries.After discussing individual preference axioms, the paper examines Pareto optimality for nonempty subsets of a feasible set in a social choice context with n voters. Aspects of simple-majority comparisons in the even-chance context follow, including an analysis of single-peaked preferences. The paper concludes with an Arrowian type impossibility theorem that is designed for the even-chance setting.     

Individual- and Contextual-Level Factors Affecting the Use of Social Support Services among Older Adults

ABSTRACT

By 2060, the number of Americans aged 65 and older is expected to more than double, while the number of Americans aged 85 and older is expected to nearly triple. As the nation's aging population grows, older adults will need to rely on social support services, such as transportation and housing services, in order to remain active and lead independent lives. In this study we use data collected from the elderly supplement of the Southeastern Pennsylvania Household Health Survey (SPHHS) (n = 3,042) to explore the relationship between the availability of elderly specific social service providers and utilization of social support services among older adults. We find that while the number of elderly specific social service providers can increase use of social support services among older adults, its impact is relatively minimal. We find that individual factors, instead, are stronger predictors of service use. This is a finding that should be particularly encouraging for elder care providers who may not have the resources needed to undertake large structural changes (like building new facilities). Still, future research should explore how the availability of a broader range of elderly specific social services (than explored in this study) impacts use.     

`Sex-Equal' Stable Matchings

The paper defines a measure on the set of stable matchings in the marriage problem. This measure is based on the minimization of the envy difference between the sets of men and women, while preserving stability and selects stable matchings with the least conflict of interest between both groups of agents. The solution concept proposed is called Sex-equal Matching (SEM) and the paper also provides an algorithm to compute the set of SEM.     

Lottery Decisions and Probability Weighting Function

This article analyzes the implications of basic lottery tests for the probability weighting function w(p). We first show that the w(p) function with one argument cannot accommodate three basic tests of lottery choice. We also discuss in detail the links between the w(p) function with one argument and the preference reversal paradox. In the last section we propose an evaluation function that accommodates the restrictions imposed by the tests and we provide an example of such function.     

What if utility functions do not exist?

Often the preferences of decision-makers are sufficiently inconsistent so as to preclude the existence of a utility function in the classical sense. Several alternatives for dealing with this situation are discussed. One alternative, that of modifying classical demands on utility functions, is emphasized and described in the context of the theory of measurement developed in recent years by behavioral scientists. The measurement theory approach is illustrated by discussing the concept of the dimension of a partial order. Even if we cannot assign numerical utility or worth values which reflect preferences in the classical utility function sense, from the measurement theory point of view we can still learn a lot about the preferences by finding several measures of worth so that a given alternative x is preferred to an alternative y if and only if x is ranked higher than y on each of the worth scales. If such measures can be found, it follows that the preferences define a partial order, and the smallest number of such scales needed is called the dimension of the partial order. If one-dimensional preferences (those amenable to classical utility assignments) cannot be found, then the next best thing is to search for partially ordered preferences with as small a dimension as possible. Several conditions under which a partial order is two-dimensional are described.The author acknowledges the helpful comments of Joel Spencer and Ralph Strauch. He also thanks Kirby Baker and Peter Fishburn for permission to quote freely from earlier joint work on two-dimensional partial orders.     

Perceptron versus automaton in the finitely repeated prisoner’s dilemma

We study the finitely repeated prisoner’s dilemma in which the players are restricted to choosing strategies which are implementable by a machine with a bound on its complexity. One player has to use a finite automaton while the other player has to use a finite perceptron. Some examples illustrate that the sets of strategies which are induced by these two types of machines are different and not ordered by set inclusion. Repeated game payoffs are evaluated according to the limit of means. The main result establishes that a cooperation at almost all stages of the game is an equilibrium outcome if the complexity of the machines the players may use is limited enough and if the length T of the repeated game is sufficiently large. This result persists when more than T states are allowed in the player’s automaton. We further consider a variant of the model in which the two players are restricted to choosing strategies which are implementable by perceptrons and prove that the players can cooperate at most of the stages provided that the complexity of their perceptrons is sufficiently reduced.     

Unemployment, Wage Pressure and Sectoral Shifts: Permanent and Temporary Consequences of Intersectoral Shocks

The main purpose of this study is to examine the effect of allocative disturbances using Italian labour market data and a VECM (vector error correction model). In order to measure sectoral shifts in labour demand, we use Neumann-Topel's [Neumann, G.R., & Topel, R.H. (1991). Employment risk, diversification, and unemployment. Quarterly Journal of Economics 106:1341–1365] employment-based dispersion index. In searching for a restricted cointegration space, we set down, and identify a stylized version of the battle of the mark-ups model. Lilien [Lilien, D. (1982). Sectoral shifts and cyclical unemployment. Journal of Political Economy 90:777–793] argued that an important part of cyclical unemployment comes from permanent shifts in the composition of labour demand. Our findings emphasize that an important source of the persistence of unemployment comes from sectoral shifts.     

Sensing Bodies and Digitally Mediated Distress

ABSTRACT

In The Five Senses (2008) Michel Serres shows how the body is not an abstracted, dislocated surface that allows for the objectification of the senses and instead illustrates how it is a process: one of continually infolding sensitivities that translate our bodily feelings into a fluid sense of the world. In this article we explore what it means to be a body in the mediated environments of everyday lives of those who visit social media sites that are designed to help people deal with mental distress. We will discuss the way that “bodies” must tack between oft-competing pressures and draws, which emanate from the performance of sense that is contained within these sites. Attempts to “make” sense of the body in such terrains often require an increasingly sophisticated set of skills and expertise and can, despite our best efforts, result in the body being transported to unexpected places. In order to capture a sense of movement, people must try to transform their offline experiences into a set of actions that can be rendered meaningful in terms of an online domain, which we argue is against the way that people sense. We develop a theory of sensory bodies as subject to continual “movement,” drawing on the work of Serres, Simondon, and Manning, before discussing three examples of social media use in mental health, and the potential implications for people having to learn to sense in and through such online spaces.     

Sensing the skin: acne sufferers and the dermatologization of life

ABSTRACT

In this paper, we explore what we call the “dermatologization of life” and how it regulates the ways in which acne sufferers relate to their skin. We refer to these ways of relating to the skin as “skin sensing”. Through an analysis of the online narratives found on the website acne.org, we demonstrate how the skin sensing bound up with dermatologization both converges with and diverges from biomedical understandings of acne in three key contexts: the hormonal, the alimentary and the nocturnal. In doing so, we show that skin sensing involves a complex combination of pleasure and pain, excitement and exhaustion, and work and play. Ultimately, we suggest that the ways in which acne sufferers sense their skin open up a set of possibilities that not only disable but also enable them as they embark on the often all-consuming quest for a clear complexion.