informational constraints and the overlapping generations model folk and anti folk theorems this paper analyses the sustainability of inter generational transfers in samuelson s consumption loan model when agents are imperfectly informed about past events we find that with mild informational constraints transfers cannot be supported by pure strategy equilibria mixed strategies allow transfers to be sustained even if agents have little information so that a version of the folk theorem holds however these equilibria are not robust if each agent s utility function is subjected to a small random perturbation as in harsanyi 1973 these mixed strategy equilibria unravel and only the zero transfer allocation survives as the unique rationalizable outcome this result is an example of mixed strategy equilibrium of an extensive form game which cannot be purified

moral hazard and private monitoring we clarify the role of mixed strategies and public randomization sunspots in sustaining near efficient outcomes in repeated games with private monitoring we study a finitely repeated game where the stage game has multiple equilibria and show that mixed strategies can support partial cooperation but cannot approximate full cooperation even if monitoring is almost perfect efficiency requires extensive form correlation where strategies can condition upon a sunspot at the end of each period for any finite number of repetitions we approximate the best equilibrium payoff under perfect monitoring assuming that monitoring is sufficiently accurate and sunspots are available journal of economic literature classification numbers c73 d82

state dependent pricing and the dynamics of money and output standard macroeconomic models of price stickiness assume that each firm leaves its price unchanged for a fixed amount of time we present an alternative model in which the pricing decision depends on the state of the economy we find a method of aggregating individual price changes that allows a simple characterization of macroeconomic variables the model produces a positive money output correlation and an empirical phillips curve in addition the impact of monetary shocks depends crucially on the current level of output which points to a natural connection between state dependent microeconomics and state dependent macroeconomics i introduction there is a long tradition in macroeconomics of attributing the real effects of nominal demand shocks to nominal price stickiness in this view if there is no change in prices when nominal demand rises then quantities must bear the burden of adjustment hence nominal price rigidity provides the friction needed for nominal demand shocks to be transmitted to the real economy standard models of this transmission mechanism such as fischer 1977 and taylor 1980 are based on the assumption that each firm leaves its price unchanged for a fixed amount of time the main reason for considering such time dependent pricing rules is their analytic tractability constraining firms to adjust their prices at prespecified times both simplifies the derivation of equilibrium strategies and allows the use of powerful time series techniques to analyze aggregate dynamics the main disadvantage of the timedependent approach is that between price adjustments firms are not allowed to respond even to extreme changes of circumstance this makes it difficult to know whether the qualitative effects of money in these models are the result of nominal rigidities per se or of the exogenously imposed pattern of price changes an alternative approach to modeling price stickiness is to allow the price setting decision to depend on the actual state of the

the behavior of prices and inflation an empirical analysis of disaggregat price data this paper analyzes the effects of inflation on the dispersion of prices as well as other aspects of price behavior using disaggregated data on prices of foodstuffs in israel during 1978 84 we find that the effect of expected inflation on intramarket price variability is stronger than the effect of unexpected inflation we show that even in times of high inflation price quotations are not trivially short and price changes are not synchronized across firms these facts taken together confirm that there is some staggering in the setting of prices we find that the distribution of real prices is far from being uniform as many menu cost based models assume or conclude in fact as inflation increases to very high levels this distribution is not even symmetric when the annual inflation rate reaches 130 percent there are equal chances of finding real prices above or below the market average but upward deviations in the real price are further away from zero than downward ones furthermore as the annu

twin dollarization and exchange rate policy abstract this paper develops a small open economy general equilibrium model with nominal rigidities to study twin dollarization in east asian economies a phenomenon where firms borrow in us dollars and also set export prices in us dollars in this model we endogenize both the currency of liability denomination and the currency of export pricing we show that a key factor that affects firms dollarization decisions is exchange rate policy twin dollarization is an optimal strategy for all firms when exchange rate flexibility is limited which implies that a fixed exchange rate regime may lead to an equilibrium with twin dollarization furthermore we find that twin dollarization can reduce the welfare loss caused by the fixed exchange rate regime as it helps to cushion the economy against domestic nominal risk

the timing and magnitude of retail store markdowns evidence from weekends and holidays we examine daily prices of eight goods at seventeen retail stores collected in ann arbor michigan over a four month period from november 1 to february 28 we focus on weekly and seasonal price patterns and on the frequency of price markdowns or sales there were frequent markdowns in the intensive shopping period prior to christmas and a tendency for such sales to occur on weekends we interpret these findings as evidence that a significant number of markdowns are timed to occur when shopping intensity is exogenously high we complement the imperfect information based motives for sales in the literature by contributing an additional element based on the role of bulk shopping and increasing returns in the shopping technology

the role of elasticity optimism in choosing an optimal currency basket with applications to israel abstract in a world in which exchange rates are floating each country must have some device for measuring the average exchange rate change whatever exchange rate policy it chooses the weight for each currency in computing such an average depends on the objective which exchange rate stabilization or change is expected to achieve if balance of trade stability is the desideratum the optimum weights optimum currency basket are shown to be a function of demand elasticities gnp trade shares etc we derive a loss function measuring the cost of using a wrong basket and compute the value of this function for our optimal israeli basket as a case study

monetary policy and exchange rate volatility in a small open economy we lay out a small open economy version of the calvo sticky price model and show how the equilibrium dynamics can be reduced to a simple representation in domestic inflation and the output gap we use the resulting framework to analyse the macroeconomic implications of three alternative rulebased policy regimes for the small open economy domestic inflation and cpi based taylor rules and an exchange rate peg we show that a key difference among these regimes lies in the relative amount of exchange rate volatility that they entail we also discuss a special case for which domestic inflation targeting constitutes the optimal policy and where a simple second order approximation to the utility of the representative consumer can be derived and used to evaluate the welfare losses associated with the suboptimal rules

sellers local currency pricing or buyers local currency pricing does it matter for international welfare analysis abstract we study international transmissions and welfare implications of monetary shocks in a two country world with multiple stages of production and multiple border crossings of intermediate goods this empirically relevant feature is important as it has opposite implications for two external spillover effects of a unilateral monetary expansion if all production and trade are assumed to occur in a single stage the conflict of interest terms of trade effect tends to dominate the common interest efficiency improvement effect for reasonable parameter values so that the international welfare effects would depend in general on the underlying assumptions about the currencies of price setting the stretch of production and trade across multiple stages of processing magnifies the efficiency improvement effect and dampens the terms of trade effect thus a monetary expansion can be mutually beneficial regardless of its source or the pricing assumptions

efficiency results in n player games with imperfect private monitoring abstract we demonstrate that efficiency is achievable in a certain class of n player repeated games with private almost perfect monitoring our equilibrium requires only one period memory and can be implemented by two state automata furthermore we show that this efficiency result holds with any degree of accuracy of monitoring if private signals are hemiindependent whereas most existing research focuses on two player cases or only a special example of n player games our results are applicable to a wide range of n player games of economic relevance such as trading goods games and price setting oligopolies

existence of nontrivial equilibria in repeated games with imperfect private monitoring abstract we consider finitely repeated games with imperfect private monitoring and provide several sufficient conditions for such a game to have an equilibrium whose outcome is different from repetition of nash equilibria of the stage game surprisingly the conditions are consistent with uniqueness of the stage game equilibrium a class of repeated chicken is shown to satisfy the condition

beliefs and private monitoring this paper develops new recursive set based methods for studying repeated games with private monitoring for any nite state strategy prole we nd necessary and sucient conditions for whether there exists a distribution over initial states such that the strategy together with this distribution form a correlated sequential equilibrium also for any given correlation device for determining initial states including degenerate cases where players initial states are common knowledge we provide necessary and sucient conditions for the correlation device and strategy to be a correlated sequential equilibrium or in the case of a degenerate correlation device for the strategy to be a sequential equilibrium we also consider several applications in these we show that the methods are computationally feasible show how to construct and verify equilibria in a secret price setting game

menu costs and the neutrality of money a model of endogenous price adjustment under money growth is presented firms follow s s pricing policies and price revisions are imperfectly synchronized in the aggregate price stickiness disappears and money is neutral the connection between firm price adjustment and relative price variability in the presence of monetary growth is also investigated the results contrast with those obtained in models with exogenous fixed timing of price adjustment

a belief based approach to the repeated prisoners dilemma with asymmetric private monitoring abstract this paper extends the belief based approach to the repeated prisoners dilemma with asymmetric private monitoring we first find that the previous belief based techniques t sekiguchi efficiency in repeated prisoners dilemma with private monitoring j econ theory 76 1997 345 361 v bhaskar i obara belief based equilibria in the repeated prisoners dilemma with private monitoring j econ theory 102 2002 40 69 cannot succeed when players private monitoring technologies are sufficiently different we then modify the previous belief based approach by letting the player with smaller observation errors always randomize between cooperate and defect along the cooperative path of the play we show that with vanishing observation errors efficiency and a folk theorem can be approximated using our modified belief based strategies

individual learning and cooperation in noisy repeated games we investigate whether two players in a long run relationship can maintain cooperation when the details of the underlying game are unknown specifically we consider a new class of repeated games with private monitoring where an unobservable state of the world influences the payoff functions and or the monitoring structure each player privately learns the state over time but cannot observe what the opponent learned we show that there are robust equilibria in which players eventually obtain payoffs as if the true state were common knowledge and players played a belief free equilibrium we also provide explicit equilibrium constructions in various economic examples copyright 2014 oxford university press

a determination of the optimal currency basket a macroeconomic analysis abstract this paper analyzes the choice of the optimal currency basket using a general equilibrium macro model of a small open economy with perfect capital mobility the optimal weights are derived to minimize the variance of domestic output the general properties of the optimal basket so obtained are identified and a number of special cases are analyzed in detail the weights are also compared with those found in the existing literature which differs from the approach here in its more partial equilibrium nature its neglect of capital flows and its focus on the stabilization of more proximate policy objectives

on failing to cooperate when monitoring is private abstract i consider a repeated prisoners dilemma where in each period each player receives an imperfect private signal about his opponent s current action i show that when players are patient enough any equilibrium where players use trigger strategies i e do not revert to cooperation once they have started defecting yields players a value arbitrarily close to the mutual minimax i also examine the robustness of the result to perturbations of the game journal of economic literature classification numbers c72

robustness of public equilibria in repeated games with private monitoring a repeated game with private monitoring is close to a repeated game with public monitoring or perfect monitoring when i the expected payoff structures are close and ii the informational structures are close in the sense that private signals in the private monitoring game can be aggregated by some public coordination device to generate a public signal whose distribution is close to the distribution of the public signal in the public monitoring game we provide a sufficient condition for the set of uniformly strict perfect public equilibria for a public monitoring game to be robust in nearby private monitoring games in the sense that they remain equilibria with respect to the public signal that is generated by such public coordination devices with truthful reporting our sufficient condition requires that every player is informationally small in a well defined sense

the output inflation trade off when prices are costly to change the output inflation trade off is investigated in a rational expectations equilibrium economy in which costly price setting makes it inefficient for agents to vary their prices at every instant it is shown that sticky prices are not some exogenous source of output fluctuation but result from the monetary policy process an economy with slow and counterinflationary money growth exhibits staggered changes in sticky prices as assumed in some new keynesian analyses an economy with fast money growth and a high degree of monetary accommodation exhibits either flexible prices or bunched frequently changing sticky prices

a near rational model of the business cycle with wage and price inertia this paper presents a model in which insignificantly suboptimal behavior causes aggregate demand shocks to have significant real effects the individual loss to agents with inertial price wage behavior is second order in terms of the parameter describing the shock while the effect on real economic variables is first order thus significant changes in business activity can be generated by anticipated money supply changes provided that some agents are willing to engage in nonmaximizing behavior which results in small losses

private monitoring in auctions abstract we study infinitely repeated first price auctions in which a bidder only learns whether or not he won the object while repetition of the stage game equilibrium is the unique nash equilibrium in public strategies with patient bidders there are simple nash equilibria in private strategies that improve on bid rotation sequential rationality is appropriately captured by essentially perfect bayesian equilibrium epbe which ignores behavior after irrelevant histories our main result is the construction of epbea that improve upon bid rotation assuming symmetry the exclusionary schemes of skrzypacz and hopenhayn tacit collusion in repeated auctions j econ theory 114 2004 153 169 including asymptotically efficient ones are supported as epbea

sticky prices new evidence from retail catalogs this paper presents new results on the size frequency and synchronization of price changes for twelve selected retail goods over the past 35 years three basic facts about the data are uncovered first nominal prices are typically fixed for more than one year although the time between changes is very irregular second prices change more often during periods of high overall inflation third when prices do change the sizes of the changes are widely dispersed both large and small changes occur for the same item and the sizes of these changes do not closely depend on overall inflation

a robust folk theorem for the prisoner s dilemma we prove the folk theorem for the prisoner s dilemma using strategies that are robust to private monitoring from this follows a limit folk theorem when players are patient and monitoring is sufficiently accurate but private and possibly independent any feasible individually rational payoff can be obtained in sequential equilibrium the strategies used can be implemented by finite randomizing automata journal of economic literature classification numbers c72 c73 d82

the optimal currency basket under vertical trade abstract this paper explores the theory of optimal currency basket in a small open economy general equilibrium model with sticky prices in contrast to existing literature we focus on an economy with vertical trade where the currencies in the basket may play different roles in invoicing trade flow in a simple two currency basket one currency is used to invoice imported intermediate goods and is called import currency while the other currency is used to invoice exported finished goods and is called export currency we find that the optimal weights of the import currency and the export currency depends critically on the structure of vertical trade moreover if a country decides to choose a single currency peg the choice of pegging currency also depends on how other competing economies respond to external exchange rate fluctuations

community enforcement of trust with bounded memory we examine how trust is sustained in large societies with random matching when records of past transgressions are retained for a finite length of time to incentivize trustworthiness defaulters should be punished by temporary exclusion however it is profitable to trust defaulters who are on the verge of rehabilitation with perfect bounded information defaulter exclusion unravels and trust cannot be sustained in any purifiable equilibrium a coarse information structure that pools recent defaulters with those nearing rehabilitation endogenously generates adverse selection sustaining punishments equilibria where defaulters are trusted with positive probability improve efficiency by raising the proportion of likely re offenders in the pool of defaulters

a limit characterization of belief free equilibrium payoffs in repeated games abstract the present paper studies repeated games with private monitoring and characterizes the set of belief free equilibrium payoffs in the limit as the discount factor approaches one and the noise on private information vanishes contrary to the conjecture by ely et al j c ely j horner w olszewski belief free equilibria in repeated games econometrica 73 2005 377 415 the equilibrium payoff set is computed by the same formula no matter how many players there are as an application of this result a version of the folk theorem is established for n player prisoner s dilemma games

exchange rates and monetary policy in emerging market economies this paper investigates the effects of exchange rate regimes and alternative monetary policy rules for an emerging market economy that is subject to a volatile external environment in the form of shocks to world interest rates and the terms of trade in particular we highlight the impact of financial frictions and the degree of exchange rate pass through in determining the relative performance of alternative regimes in stabilizing the economy in the face of external shocks our results are quite sharp when exchange rate pass through is high a policy of non traded goods inflation targeting does best in stabilizing the economy and is better in welfare terms when exchange rate pass through is low however a policy of strict cpi inflation targeting is better in all cases a fixed exchange rate is undesirable in addition financial frictions have no implications for the ranking of alternative policy rules

monopolistic competition and the effects of aggregate demand how important is monopolistic competition to an understanding of the effects of aggregate demand on output we ask the question at three levels can monopolistic competition by itself explain why aggregate demand movements affect output can it together with other imperfections generate effects of aggregate demand in a way that perfect competition cannot if so can it give an accurate account of the response of the economy to aggregate demand movements the answers are no yes and yes

the magnitude of menu costs direct evidence from large u s supermarket chains we use store level data to document the exact process of changing prices and to directly measure menu costs at five multistore supermarket chains we show that changing prices in these establishments is a complex process requiring dozens of steps and a nontrivial amount of resources the menu costs average 105 887 year per store comprising 0 70 percent of revenues 35 2 percent of net margins and 0 52 price change these menu costs may be forming a barrier to price changes specifically 1 a supermarket chain facing higher menu costs due to item pricing laws that require a separate price tag on each item changes prices two and one half times less frequently than the other four chains 2 within this chain the prices of products exempt from the law are changed over three times more frequently than the products subject to the law in principle fixed costs of changing prices can be observed and measured in practice such costs take disparate forms in different firms and we have no data on their magnitude so the theory can be tested at best indirectly at worst not at all alan blinder 1991 p 90

introduction to repeated games with private monitoring abstract we present a brief overview of recent developments in discounted repeated games with imperfect private monitoring the literature explores the possibility of cooperation in a long term relationship where each agent receives imperfect private information about the opponents actions although this class of games admits a wide range of applications such as collusion under secret price cutting exchange of goods with uncertain quality and observation errors it has fairly complex mathematical structure due to the lack of common information shared by players this is in sharp contrast to the well explored case of repeated games under public information with the celebrated folk theorems and until recently little had been known about the private monitoring case however rapid developments in the past few years have revealed the possibility of cooperation under private monitoring for some class of games journal of economic literature classification numbers c72 c73 d43 d82 l13 l41

optimal pricing with costly adjustment evidence from retail grocery prices in many theoretical models it is assumed that there are costs associated with adjusting prices in this paper the existence type and magnitude of such costs are investigated empirically a discrete choice dynamic programming model that nests fixed and variable costs is developed and econometric estimates of the adjustment cost function are obtained the data used to implement the model consist of weekly retail prices and sales of three brands of saltine crackers sold by four chains of grocery stores in a small u s town the study has several distinguishing characteristics first the data are highly disaggregate at the level of brand and store second variables are sampled at weekly intervals third the model nests fixed and variable adjustment costs and can therefore determine their relative importance finally the discrete choice model is both structural and dynamic

aggregation and optimization with state dependent pricing the literature on the aggregation of s s policies has ignored the impact of aggregate behavior on the individual s optimization problem in the case of pricing the feedback effects are clear not only do pricing strategies determine the evolution of the price level but the evolution of the price level also influences the optimal pricing strategies in this paper we provide a consistent treatment of aggregation and optimization we use this model to analyze three issues in the menu cost pricing literature the relationship between strategic complementarity and the real effects of money the relationship between the variance of the money supply and the correlation between money and output and the relationship between the cost of price adjustment and the size of price adjustment questions concerning the dynamics of aggregate variables such as prices employment investment and consumption represent the core of business cycle analysis one striking feature of these variables is the radical difference between properties of these aggregates and the nature of the individual behavior that underlies them the behavior of a firm s prices investment and employment and the behavior of an individual s consumption all involve frictional elements that lead to discrete adjustment at the microeconomic level heterogeneity among individuals however tends to smooth the behavior of the corresponding aggregates in recent years a large body of research has developed to examine the manner in which microeconomic frictions influence aggregate dynamics one of the centerpieces of this research has been the s s model developed by arrow harris and marschak 1951 the key element of this model is the state dependence of individual decisions agents act when a state variable crosses some critical threshold which balances the cost and benefits of adjustment the aggregate implications of this form of microeconomic behavior have been analyzed by blinder 1981 caplin 1985 and mosser 1991 in the context of inventory dynamics by caplin and spulber 1987 caballero and engel 1991 1993 and caplin and leahy 1991 in the context of prices and by bertola and caballero 1990 caballero 1993 and eberly 1994 in the context of con sumer durables one of the most limiting aspects of these models is that they focus exclusively on the impact that microeconomic inertia has on aggregate dynamics they 1we would like to thank michael harrison loannis karatzas john leahy sr andreu mas colell a co editor and four anonymous referees for helpful discussions and comments and the national science foundation and the sloan foundation for financial support

repeated games with private monitoring two players we investigate two player infinitely repeated games where the discount factor is less than but close to unity monitoring is private and players cannot communicate we require no condition concerning the accuracy of players monitoring technology we show the folk theorem for the prisoners dilemma with conditional independence we also investigate more general games where players private signals are correlated only through an unobservable macro shock we show that efficiency is sustainable for generic private signal structures when the size of the set of private signals is sufficiently large finally we show that cartel collusion is sustainable in price setting duopoly

what is new keynesian economics this research was supported by the national science foundation i am grateful to george williams for help with the data and to steven allen laurence ball olivier j blanchard timothy bresnahan charles calomiris dennis carlton robert chirinko russell cooper stanley fischer herschel grossman r glenn hubbard david laidler john leahy assar lindbeck n gregory mankiw david romer julio rotemberg dennis snower john taylor andrew weiss and two anonymous referees for comments on one or more earlier drafts i am also indebted to michael parkin and edmund s phelps for helping to establish the etymology of the phrase new keynesian

the repeated prisoner s dilemma with imperfect private monitoring abstract in this paper i study a repeated prisoner s dilemma game in which monitoring is private and imperfect a partial folk theorem is proved for the case of almost perfect monitoring

small menu costs and large business cycles a macroeconomic model of monopoly i introduction the conflict between modern neoclassical and traditional keynesian theories of the business cycle centers upon the pricing mechanism in neoclassical models prices are fully flexible they represent the continuous optimization of economic agents and the continuous intersection of supply and demand in keynesian models prices are often assumed to be sticky they do not necessarily equilibrate all markets at all times one of the reasons for the resurgence of the equilibrium approach to macroeconomics has been the absence of a theoretical underpinning for this keynesian price stickiness this note shows that sticky prices can be both privately efficient and socially inefficient the business cycle results from the suboptimal adjustment of prices in response to a demand shock to the extent that policy can stabilize aggregate demand it can mitigate the social loss due to this suboptimal adjustment in some keynesian models prices are simply exogenously fixed 2 in others agents must set their prices in advance of the transaction date the act of altering a posted price is certainly costly these costs include such items as printing new catalogs and informing salesmen of the new price yet these menu costs are small and therefore generally perceived as providing only a weak foundation for these fixed price models however this inference is flawed small menu costs can cause large welfare losses the claim that price adjustment costs are small does not rebut the claim that they are central to understanding economic fluctuations

belief based equilibria in the repeated prisoners dilemma with private monitoring abstract we analyze repeated prisoners dilemma games with imperfect private monitoring and construct mixed trigger strategy equilibria such strategies have a simple representation where a player s action only depends upon her belief that her opponent s are continuing to cooperate when monitoring is almost perfect the symmetric efficient outcome can be approximated in any prisoners dilemma game while every individually rational feasible payoff can be approximated in a class of such games the efficiency result extends when there are more than two players it requires that monitoring be sufficiently accurate but does not require very low discounting when a public randomization device is available journal of economic literature classification numbers c73 d82

experiments with the optimal currency composite this paper addresses the issue of the determination of an optimal currency composite in the context of a world characterized by generalized exchange rate flexibility the approach adopted here is macroeconomic in nature and stresses general equilibrium considerations the emphasis upon both monetary and real considerations capital mobility and rational expectations in the context of a multi country framework is what sets this paper apart from previous attempts to address this issue empirically the problem of choosing an optimal currency composite has if anything gained importance according to the annual report on exchange arrangements issued by the international monetary fund as many as 37 countries were reported to be practicing currency basket arrangements during 1980 81 while a year later i e 1981 82 the number of such countries had increased to 53 see annual report june 3 1983 as indicated in the annual report this increase can be attributed to the movement away from single currency dollar pegs in favor of increased use of currency composites including the sdr pg 9 the advantage of a composite peg over a single currency peg is clear a composite peg embodies automatic and systematic adjustment of bilateral exchange rates whenever necessary which may be preferable to an absolute peg against all currencies or to joint floating as implied by a single currency peg the latter arrangement may subject the economy in question to an undesirable degree of exchange rate volatility while the former carries with it heavy intervention costs thus the composite currency peg has proved to be an acceptable middle ground for economies as different as sweden and india in practice the shares assigned to various currencies comprising the basket where such arrangements have been maintained have usually been determined on the basis of the currency composition of the economy s international trade the appendix provides some institutional details regarding the weighting practices of the 53 currency composite countries over the period 1981 82 as indicated here 32 countries peg their currencies to a basket whose currency shares are determined in accordance with bilateral trade patterns of the economy in question an additional 21 countries peg their currencies to the sdr which is itself a 5 currency basket with the weights being set by the imf by reference to the currency denomination of world trade theoretical analysis of the composition of the optimal basket owes much to flanders and helpman 8 9 whose work is extended by

the folk theorem for repeated games with observation costs abstract the folk theorem literature has been relaxing the assumption on how much players know about each other s past action here we consider a general model where players can buy precise information every period each player decides whether to pay a cost to accurately observe the actions chosen by other players in the previous period when a player does not pay the cost he obtains only imperfect private signals observational decisions are unobservable to others known strategies such as trigger strategies do not work since they fail to motivate players to pay for information this paper shows that the folk theorem holds for any level of observation costs unlike existing folk theorems with private monitoring ours imposes virtually no restriction on the nature of costless imperfect signals the theorem does not use explicit or costless communication thereby having implications on antitrust laws that rely on evidence of explicit communication the main message is that accurate observation alone however costly enables efficient cooperation in general repeated games

efficiency in repeated prisoner s dilemma with private monitoring abstract this paper analyzes repeated games with private monitoring where in each period each player receives a signal of the other player s action in the previous period and that signal is private information previous literature on discounted repeated games with private monitoring has not shown whether or not nearly efficient equilibria exist for a repeated prisoner s dilemma satisfying a certain assumption regarding stage game payoffs we show that there exists a nearly efficient sequential equilibrium provided that imperfectness of signals is small and players are patient journal of economic literature classification number c73