when does communication improve coordination we study costless pre play communication of intentions among inexperienced players using the level k model of strategic thinking to describe players beliefs we fully characterize the effects of preplay communication in symmetric 2 2 games one way communication weakly increases coordination on nash equilibrium outcomes although average payoffs sometimes decrease two way communication further improves payoffs in some games but is detrimental in others moving beyond the class of symmetric 2 2 games we find that communication facilitates coordination in common interest games with positive spillovers and strategic complementarities but there are also games in which any type of communication hampers coordination jel c72 d83

screening ethics when honest agents care about fairness we analyze a principal s ability to discriminate between honest and dishonest agents who have private information about the circumstances of the exchange honest agents reveal circumstances truthfully as long as the mechanism is suciently fair the probability that an equilibrium allocation is chosen by an agent who is lying should not be too large without intolerance for lying the agent is given proper incentives if dishonest and zero rent if honest with even a small intolerance for lying the optimal mechanism is discontinuously altered it may still involve ethics screening whereby some allocation chosen by a dishonest agent is never chosen by an honest agent it happens either when the dishonest is overstating circumstances or when the principal is forced to allow for some suboptimal announcements due to an excessive intolerance for lying with limited intolerance for lying ethics screening allows for doing better than in the standard setup where the agent is dishonest with certainty even if honesty is unlikely however if intolerance for lying is too strong the principal cannot improve upon the standard setup

evolutionary stability in games of communication abstract this paper identifies evolutionarily stable outcomes in games in which one player has private information and the other takes a payoff relevant action the informed player can communicate at little cost outcomes satisfying a set valued evolutionary stability condition must exist and be efficient in common interest games when there is a small cost associated with using each message the outcome preferred by the informed player is stable the paper introduces a nonequilibrium set valued stability notion of entry resistant sets for games with partial common interest the no communication outcome is never an element of an entry resistant set journal of economic literature classification numbers c72 d82

the impact of biogas technology adoption for farm households empirical evidence from mixed crop and livestock farming systems in indonesia abstract this paper aims to study the impact of biogas technology adoption as a livestock waste technology to support mixed crop and livestock mcl farming among smallholder farmers in indonesia a cross sectional survey was conducted to collect data from 351 farm households 171 biogas adopters and 180 non adopters in the province of yogyakarta this study employed treatment effects analysis based on propensity score matching techniques to evaluate the impacts of biogas technology adoption among the farm households the results showed that the adoption of the biogas technology reduces firewood consumption of smallholder farm households in indonesia unfortunately the impact on the use of slurry for organic fertilizers and the use of gas liquid petroleum gas lpg as another household cooking energy could not be evaluated this study empirically showed that the benefits of the biogas technology had not yet been optimized at the household level which may partly explain the slow rate of biogas technology diffusion among farmers however the consumption reduction of firewood as a benefit of using biogas contributed to behavioral changes of the women in the households especially with respect to firewood collection and cooking activities

an experimental study of truth telling in a sender receiver game a recent experimental study of cai and wang 2005 on strategic information transmission reveals that subjects tend to transmit more information than predicted by the standard equilibrium analysis to evidence that this overcommunication phenomenon can be explained in terms of a tension between normative social behavior and incentives for lying we show in a simple sender receiver game that subjects incurring in costs to punish liars tell the truth more often than predicted by the logit agent quantal response equilibria whereas subjects that do not punish liars after receiving a deceptive message play on the aggregate equilibrium strategies thus we can partition the subject pool into two groups one group of subjects with preferences for truth telling and one taking into account only material incentives

meaning and credibility in cheap talk games i define neologism proofness a refinement of perfect bayesian equilibrium in cheap talk games it applies when players have a preexisting common language so that an unexpected message s literal meaning is clear and only credibility restricts communication i show that certain implausible equilibria are not neologism proof in some games no equilibrium is journal of economic literature classification numbers d83 d82 c73

biogas energy from family sized digesters in uganda critical factors and policy implications dependence on fossil energy sources is increasingly becoming unsustainable due to ecological and environmental problems and rapid depletion biogas energy could augment these conventional energy sources but despite its advantages and favourable conditions for its production biogas energy use in uganda remains low due to technical economic and socio cultural impediments based on primary data on households in central and eastern uganda and the use of logistic regression this study analyses factors affecting the adoption of biogas energy in uganda the empirical results suggest that the probability of a household adopting biogas technology increases with decreasing age of head of household increasing household income increasing number of cattle owned increasing household size male head of household and increasing cost of traditional fuels in contrast the likelihood of adoption decreases with increasing remoteness of household location and increasing household land area policy options and recommendations including educational and awareness campaigns on biogas benefits and successes the provision of financial and non financial incentives to households and establishment of an institutional framework could bolster wider biogas energy acceptance in uganda

trade and invasive species risk mitigation reconciling wto compliance with maximising the gains from trade abstract this paper analyses the issue of balancing the gains from trade with the risk of pest and disease transference two decision frameworks for determining whether or not to permit trade in a potentially invasive species carrying good are presented the first considers only the potential production losses resulting from an invasive species entering through a trade pathway as is prescribed by wto compliance the second is a unilateral welfare maximising approach which considers the consumer gains from trade the loss of domestic producers market share and expected damage from the invasive species it is shown that these alternative decision frameworks can be reconciled such that they produce the same outcome regarding whether or not trade is to be permitted the key parameters which influence these decisions are also highlighted

promises and endogenous reneging costs we present a novel theoretical mechanism that explains the capacity for non enforceable communication about future actions to improve efficiency we explore a two player partnership game where before choosing a level of effort to exert on a joint project each player makes a cheap talk promise to their partner about their own future effort we allow agents to incur a psychological cost of reneging on their promises we demonstrate a strong tendency for evolutionary processes to select agents who incur intermediate costs of reneging and show that these intermediate costs induce second best optimal outcomes

a theory of credibility this paper presents models in which one agent must decide whether to trust another whose motives are uncertain reliability can only be communicated through actions in this context it pays for people to build a reputation based on reliable behaviour someone becomes credible by consistently providing accurate and valuable information or by performing useful services the theory provides a justification for long term arrangements without binding contracts it also describes those situations where it pays an agent to cash in on his reputation many decisions depend on trusting someone consumers must decide whether to believe advertisements banks need to judge the reliability of loan applicants and employers must decide how much responsibility to delegate to their employees this paper attempts to model situations that arise when someone is uncertain about whether to trust the people he deals with in this context reputations for reliability are valuable an agent becomes credible by consistently providing accurate valuable information or by always acting responsibly i analyse a series of simple abstract models of information transmission in the basic model there are two agents the sender s and the receiver r who are to play the game a known finite number of times at each stage both players learn the value of a parameter measuring the importance of that period s play of the game that is the value of making a correct decision and s obtains payoff relevant information s then sends a signal to r who makes a decision that affects the welfare of both players after both players learn the consequences of r s decision the process repeats at each stage r must decide what action to take in order to do that he must assess the credibility of s the difficulty arises because r is uncertain about s s preferences when play begins i model this by assuming that with positive probability s has identical preferences to r s is a friend and with positive probability s has completely opposed preferences to r s is an enemy this uncertainty creates a trade off for enemy senders at each stage providing honest information enhances s s reputation but only at the expense of foregoing an opportunity for immediate gain by duping r the possibility that s is a friend lends credibility to what he says but this credibility may also be exploited by an enemy s the principal equilibrium has the following form in the basic model where s has no control over the importance of a given play s typically conveys accurate information for the first several periods r raises the probability he places on s being friendly after receiving accurate information if he believes that an enemy would have lied to him with positive probability the more important the information the more likely an enemy will attempt to deceive r an enemy will eventually take advantage of r by misleading him when this happens the sender loses all opportunities for deception in the future i

costly predation and the distribution of competence an evolutionary game model shows how an equilibrium distribution of competence may evolve when members of a population prey on one another but when predatory competence is costly to acquire under one interpretation the competence distribution is an endogenously determined distribution of bounded rationality an example shows how tricksters and suckers might coexist in the long run the analysis leads to a curious result about a mixed equilibrium for a symmetric zero sum game an increase in the costs of one or more competence levels has exactly zero effect on the fraction of the population at those levels

exploring the regional implications of interstate quarantine policies in western australia abstract as a signatory of the world trade organization agreement australia has a responsibility to ensure the behaviour of its internal markets for food and food related products abide by the same rules and regulations as international trade this has generated a need to demonstrate the validity of any measures that restrict competition to avoid disputes and or retaliatory actions by other signatories this paper explores a spatial economic evaluation technique that can be used to examine the welfare implications of quarantine policies for regionalised industries and demonstrates practical application of this technique using two case studies of interstate trade within australia

in and out of equilibrium ii evolution in repeated games with discounting and complexity costs abstract we explore evolutionary dynamics for repeated games with small but positive complexity costs we begin by extending a folk theorem result by cooper 1996 to continuation probabilities or discount rates smaller than 1 then we show that all d has a uniform invasion barrier since none of the more cooperative equilibria are robust against indirect invasions we might expect not to observe any cooperative equilibria when complexity costs are positive the average level of cooperation in the dynamics however can hover anywhere between no cooperation at all and the average level of cooperation in the absence of complexity costs depending on how small complexity costs are and how large the population is

a review on biogas technology and its contributions to sustainable rural livelihood in ethiopia abstract biogas technology has uneven dissemination over the globe the technology is at its infant stage of development and dissemination in many developing countries while china has the largest implementation record the principal factors controlling its dissemination include policies and institutions financial constraint subsidies availability of inputs awareness about the technology consumers considerations and success stories about the technology however biogas technology is a multipurpose technology which assists in addressing economic health social and environmental problems simultaneously thus development and dissemination of the technology certainly minimize energy poverty and improve peoples status in the energy ladder in line with this ethiopia has completed implementing the first phase 2009 2013 of its national biogas programme and has started implementing its second phase during the first phase it was able to disseminate 57 6 the total 14 000 domestic biogas plants planned for the period though the technology was introduced about five decades ago into the country biogas installations constructed prior to the establishment of the national biogas programme were having varied digester models lacked standards and central coordination and their entire number was not more than 1000 this paper reviews the status of dissemination of household biogas technology factors influencing the dissemination of the technology benefits of the technology at global scales energy resources consumption patterns and brief account of the technology at national scale ethiopia

there is no silver bullet the value of diversification in planning invasive species surveillance abstract in this study we demonstrate how the notion of diversification can be used in broad scale resource allocation for surveillance of invasive species we consider the problem of short term surveillance for an invasive species in a geographical environment we find the optimal allocation of surveillance resources among multiple geographical subdivisions via application of a classical portfolio framework which allocates investments among multiple financial asset types with uncertain returns in a portfolio that maximizes the performance and by meeting the desired diversification targets protects against errors in estimating the portfolio s performance we illustrate the approach with a case study that applies a spatial transmission model to assess the risk of spread of the emerald ash borer eab a significant pest in north america with infested firewood that may be carried by visitors to campground facilities in central canada adding the diversification objective yields an expected survey performance that is comparable with undiversified optimal allocation but more importantly makes the geographical distribution of survey priorities less subject to possible errors in the spread rate estimates overall diversification of pest surveillance can be viewed as a viable short term strategy for hedging against uncertainty in expert and model based assessments of pest invasion risk

cheap talk with two audiences these problems have in common a simple structure an informed sender says something to two interested but uninformed receivers who then take actions based on their beliefs these actions affect the sender as well as the receivers in this paper we study how costless nonverifiable claims cheap talk can affect these beliefs and hence the actions and how the incentives for truthful revelation to one receiver are affected by the presence of the other we then ask how welfare is affected by whether claims are made in public or in private as some of the above examples suggest public messages may be more credible than private messages addressed to either audience one possibility is that the presence of one audience can discipline the sender s relationship with the other we call this one sided

agricultural technology crop income and poverty alleviation in uganda summary this paper evaluates the ex post impact of adopting improved groundnut varieties on crop income and poverty in rural uganda the study utilizes cross sectional data of 927 households collected in 2006 from seven districts in uganda using propensity score matching methods we find that adopting improved groundnut varieties technology significantly increases crop income and reduces poverty the positive and significant impact on crop income is consistent with the perceived role of new agricultural technologies in reducing rural poverty through increased farm household income this study supports broader investment in agriculture research to address vital development challenges reaching the poor with better technologies however requires policy support for improving extension efforts access to seeds and market outlets that simulate adoption

language meaning and games a model of communication coordination and evolution comment demichelis and weibull 2008 aer show that adding lexicographic lying costs to coordination games with cheap talk yields a sharp prediction only the efficient outcome is evolutionarily stable i show that this result is caused by the discontinuity of preferences rather than by small lying costs per se finally i discuss why discontinuity may not be an appealing assumption in evolutionary models

evolutionary stability and lexicographic preferences abstract we explore the interaction between evolutionary stability and lexicographic preferences to do so we define a limit nash equilibrium for a lexicographic game as the limit of nash equilibria of nearby games with continuous preferences nash equilibria of lexicographic games are limit nash equilibria but not conversely modified evolutionarily stable strategies binmore and samuelson 1992 j econ theory 57 278 305 are limit nash equilibria modified evolutionary stability differs from lexicographic evolutionarily stability defined by extending the common characterization of evolutionary stability to lexicographic preferences in the order in which limits in the payoff space and the space of invasion barriers are taken

agricultural technology adoption and poverty reduction a propensity score matching analysis for rural bangladesh this study aims at shedding some light on the potential impact of agricultural technology adoption on poverty alleviation strategies it does so through an empirical investigation of the relationship between technological change of the green revolution type and wellbeing of smallholder farm households in two rural bangladeshi regions as technology adoption is not randomly assigned but there is self selection into treatment the paper tackles a methodological issue in assessing the causal effect of technology on farm household wellbeing through the non parametric p score matching analysis it pursues a targeted evaluation of whether adopting a modern seed technology causes resource poor farmers to improve their income and decrease the propensity to fall below the poverty line it finds a robust and positive effect of agricultural technology adoption on farm household wellbeing suggesting that there is a large scope for enhancing the role of agricultural technology in directly contributing to poverty alleviation 2006 elsevier ltd all rights reserved

promises and conventions an approach to pre play agreements abstract i analyze how informal agreements can be sustained by moral emotions with regard to a large class of two player games specifically i assume that people feel guilty if they breach an agreement and that the guilt increases according to the degree of the harm inflicted on the other a central insight is that it is easier to sustain efficient informal agreements if actions are strategic complements than if they are strategic substitutes i complement this general insight by studying two specific cases where negotiators face uncertainty about the breach of the agreement i show that while the optimal agreement in a game with strategic substitutes must compromise on surplus maximization and efficiency the optimal agreement in a game with sufficiently strong strategic complements tends to maximize both the surplus and the probability of compliance especially if the game is symmetric

the impact of improved maize varieties on poverty in mexico a propensity score matching approach summary this study examines the adoption of improved maize germplasm in oaxaca and chiapas in mexico it employs a propensity score matching approach to analyze the impact of the adoption of improved maize varieties on household income and poverty reduction using cross sectional data of 325 farmers from the two regions the findings reveal a robust positive and significant impact of improved maize variety adoption on farm household welfare measured by per capita expenditure and poverty reduction specifically the empirical results suggest that adoption of improved maize varieties helped raise household per capita expenditure by an average of 136 173 mexican pesos thereby reducing their probability of falling below the poverty line by roughly 19 31

evolutionary drift and equilibrium selection this paper develops an approach to equilibrium selection in game theory based on studying the learning process through which equilibrium is achieved the differential equations derived from models of interactive learning typically have stationary states that are not isolated instead nash equilibria that specify different out of equilibrium behaviour appear in connected components of stationary states the stability properties of these components can depend critically on the perturbations to which the system is subjected we argue that it is then important to incorporate such drift into the model a sufficient condition is provided for drift to create stationary states with strong stability properties near a component of equilibria applications to questions of forward and backward induction are developed

evolution of preferences we endogenize preferences using the indirect evolutionary approach individuals are randomly matched to play a two person game individual subjective preferences determine their behaviour and may differ from the actual objective pay offs that determine fitness matched individuals may observe the opponents preferences perfectly not at all or with some in between probability when preferences are observable a stable outcome must be efficient when they are not observable a stable outcome must be a nash equilibrium and all strict equilibria are stable we show that for pure strategy outcomes these conclusions are robust to allowing almost perfect and almost no observability with the notable exception that inefficient strict equilibria may fail to be stable with any arbitrarily small degree of observability despite being stable with no observability

language meaning and games a model of communication coordination and evolution language is a powerful coordination device we generalize the cheap talk approach to pre play communication by way of introducing a meaning cor respondence between messages and actions and by postulating two axioms met by natural languages players have a lexicographic preference second to material payoffs against deviating from the meaning correspondence under two sided communication in generic and symmetric n 3 n coordination games a nash equilibrium component in such a lexicographic communication game is evolutionarily stable if and only if it results in the unique pareto efficient out come of the underlying game we extend the analysis to one sided communica tion in arbitrary finite two player games jel c72 c73 z 3

commitment and conflict in bilateral bargaining building on crawford 1982 we study a model of bilateral bargaining in which negotiators can make binding commitments at a low positive cost c our primary solution concept is iterated strict dominance if commitment attempts never fail there are three solutions in two solutions all the surplus goes to one player in the third solution there is a high probility of con ict if commitment attempts succeed with probability q 1 the unique solution entails con ict with probability q 2 when c 0 analogous results hold if the requirement of iterated strict dominance is replaced by iterated weak dominance

social stability and equilibrium in the field of noncooperative game theory nash equilibrium nash 1951 has played a central role as a solution concept in bold strokes one may discern two major interpretations of nash equilibrium in the context of rational players the first which is close to the eductive interpretation of binmore 1987 1988 and the complete information interpretation of kaneko 1987 assumes that the game is played exactly once if it is a repeated game the repetition occurs once and the players have sufficient knowledge and ability to analyze the game in a rational manner sometimes it is assumed that all players have consistent hierarchies of beliefs where the game and their priors are common knowledge bayesian interpretation such as proposed by aumann 1987 advanced this idea to the level that the players have a common prior from this point of view however nash equilibrium seems far from being satisfactory

adverse selection and entrepreneurship in a model of development this paper presents a theory in which talented entrepreneurs are identified as the key agents driving the process of development and modernisation entrepreneurial skills are private information which prevents full risk sharing development into a modern industrial economy might fail to take place since potentially talented entrepreneurs may refrain from taking on the entrepreneurial risks as a way to avoid income shocks an interesting feature of the model is the fact that the informational asymmetries are endogenous to the process of development as they are related to the heterogeneity in entrepreneurial skills required in the manufacturing activities

an evolutionary approach to pre play communication we add a round of pre play communication to a finite two player game played by a population of players pre play communication is cheap talk in the sense that it does not directly enter the payoffs the paper characterizes the set of strategies that are stable with respect to a stochastic dynamic adaptive process periodically players have an opportunity to change their strategy with a strategy that is more successful against the current population any strategy that weakly improves upon the current poorest performer in the population enters with positive probability when there is no conflict of interest between the players only the efficient outcome is stable with respect to these dynamics for general games the set of stable payoffs is typically large every efficient payoff recurs infinitely often

alternative time patterns of decisions and dynamic strategic interactions this paper offers a simple approach to study steady state markov perfect equilibria arising in dynamic games when players are obliged to commit their actions for several periods it highlights the importance of spillovers and dynamic strategic interactions when assessing the various time patterns conceivable in such games the obtained results are then applied to various either micro or macroeconomic issues where time patterns of decisions matter

two questions about european unemployment a general equilibrium search model makes layoff costs affect the aggregate unemployment rate in ways that depend on equilibrium proportions of frictional and structural unemployment that in turn depend on the generosity of government unemployment benefits and skill losses among newly displaced workers the model explains how before the 1970s lower flows into unemployment gave europe lower unemployment rates than the united states and also how after 1980 higher durations have kept unemployment rates in europe persistently higher than in the united states these outcomes arise from the way europe s higher firing costs and more generous unemployment compensation make its unemployment rate respond to bigger skill losses among newly displaced workers those bigger skill losses also explain why u s workers have experienced more earnings volatility since 1980 and why especially among older workers hazard rates of gaining employment in europe now fall sharply with increases in the duration of unemployment

social norms and economic incentives in firms abstract this paper studies the interplay between economic incentives and social norms in firms we introduce a general framework to model social norms arguing that norms stem from agents desire for or peer pressure towards social efficiency in a simple model of team production we examine the interplay of three types of contracts with social norms we show that one and the same norm can be output increasing neutral or output decreasing depending on the contract multiplicity of equilibria and crowding out effects of steeper incentives can arise

special interests and the media theory and an application to climate change a journalist reports to a voter on an unknown policy relevant state competing special interests can make claims that contradict the facts but seem credible to the voter a reputational incentive to avoid taking sides leads the journalist to report special interests claims to the voter in equilibrium the voter can remain uninformed even when the journalist is perfectly informed communication is improved if the journalist discloses her partisan leanings the model provides an account of persistent public ignorance on climate change that is consistent with narrative and quantitative evidence

strategic communication with lying costs i study a model of strategic communication between an uninformed receiver and an informed but upwardly biased sender the sender bears a cost of lying or more broadly of misrepresenting his private information the main results show that inflated language naturally arises in this environment where the sender almost always claims to be of a higher type than he would with complete information regardless of the intensity of lying cost there is incomplete separation with some pooling on the highest messages the degree of language inflation and how much information is revealed depend upon the intensity of lying cost the analysis delivers a framework to span a class of cheap talk and verifiable disclosure games unifying the polar predictions they make under large conflicts of interest i use the model to discuss how the degree of manipulability of information can affect the trade off between delegation and communication copyright 2009 wiley blackwell

communication coordination and nash equilibrium i note a methodological problem in studying the role of pre play communication in ensuring equilibrium to deal with this problem i define a solution concept for the extended game in which talk is followed by play that is intermediate between nash equilibrium and rationalizability in some games our solution concept implies a nash outcome while in others it does not

using privileged information to manipulate markets insiders gurus and credibility access to private information is shown to generate both the incentives and the ability to manipulate asset markets through strategically distorted announcements the fact that privileged information is noisy interferes with the public s attempts to learn whether such announcements are honest it allows opportunistic individuals to manipulate prices repeatedly without ever being fully found out this leads us to extend sobel s 1985 model of strategic communication to the case of noisy private signals our results show that when truthfulness is not easily verifiable restrictions on trading by insiders may be needed to preserve the integrity of information embodied in prices

lying for strategic advantage rational and boundedly rational misrepresentation of intentions starting from hendricks and mcafee s 2000 example of the allies decision to feint at calais and attack at normandy on d day this paper models misrepresentation of intentions to competitors or enemies allowing for the possibility of bounded strategic rationality and rational players responses to it yields a sensible account of lying via costless noiseless messages in many cases the model has generically unique pure strategy sequential equilibria in which rational players exploit boundedly rational players but are not themselves fooled in others the model has generically essentially unique mixed strategy sequential equilibria in which rational players strategies protect all players from exploitation