peer group formation in an adverse selection model this paper develops an adverse selection model where peer group systems are shown to trigger lower interest rates and remove credit rationing in the case where borrowers are uninformed about their potential partners and ex post state verification or auditing by banks is costly peer group formation reduces interest rates due to a collateral effect namely cross subsidisation amongst borrowers acts as collateral behind a loan by uncovering such a collateral effect this paper shows that peer group systems can be viewed as an effective risk pooling mechanism and thus enhance efficiency notjust in the full information set up a well known family of adverse selection models in the stiglitz and weiss 1981 tradition demonstrates that when banks are imperfectly informed about the riskiness of borrowers projects and therefore cannot discriminate against risky borrowers interest rates become inefficiently high and worthy borrowers are driven out of the credit market the extent of this problem is substantially magnified when borrowers do not have adequate collateral to secure a loan typically adverse selection combined with lack of collateral leads to prohibitively high interest rates poorly endowed individuals e g students immigrants the unemployed and a vast majority of poor individuals in developing countries often face such high rates and therefore cannot take advantage of profitable investment opportunities a peer group formation system represents a possible solution to the above problem under this system a bank lends to borrowers without collateral on condition that the borrowers organise themselves into groups and that participant borrowers within each group accept to take joint responsibility for a loan thus in addition to repaying their own share of the loan each group member must accept to repay the obligations of their defaulting peers otherwise the entire group is denied access to future refinancing systems of this kind have been very successful in practice they have generated lower interest rates for the rural poor in for example bangladesh the philippines bolivia and the state of arkansas in the united states moreover group lending has also been successfully implemented in large urban areas such in the cities of dhaka and chicago 1

efficient mechanisms for bilateral trading we consider bargaining problems between one buyer and one seller for a single object the seller s valuation and the buyer s valuation for the object are assumed to be independent random variables and each individual s valuation is unknown to the other we characterize the set of allocation mechanisms that are bayesian incentive compatible and individually rational and show the general impossibility of ex post efficient mechanisms without outside subsidies for a wide class of problems we show how to compute mechanisms that maximize expected total gains from trade and mechanisms that can maximize a broker s expected profit journal of economic literature classification number 026

the microfinance promise in the past decade microfinance programs have demonstrated that it is possible to lend to low income households while maintaining high repayment rates even without requiring collateral the programs promise a revolution in approaches to alleviating poverty and spreading financial services and millions of poor households are served globally a growing body of economic theory demonstrates how new contractual forms offer a key to microfinance success particularly the use of group lending contracts with joint liability for the most part however high repayment rates have not translated into profits and studies of impacts on poverty yield a mixed picture in describing emerging tensions the paper highlights the diversity of innovative mechanisms beyond group lending contracts the measurement of financial sustainability the estimation of economic and social impacts the costs and benefits of subsidization and the potential to reduce poverty through savings programs rather than just credit the promise of microfinance has pushed far ahead of the evidence and an agenda is put forward for addressing critical empirical gaps and sharpening the terms of policy discussion

robust trading mechanisms we consider the problem of designing a trading institution for a single buyer and seller when their valuation of the good is private information it is shown that posted price mechanisms are essentially the only mechanisms such that each trader has a dominant strategy a posted price mechanism is one where a price is posted in advance and trade occurs if and only if all traders agree to trade

club good intermediaries abstract the emergence and ubiquitous presence in everyday life of digital goods such as songs movies and e books give renewed salience to the problem of providing public goods with exclusion because digital goods are typically traded via intermediaries like itunes amazon and netflix the question arises as to the optimal pricing mechanism for such club good intermediaries we derive the direct bayesian optimal mechanism for allocating club goods when the mechanism designer is an intermediary that neither produces nor consumes the goods and we develop an indirect mechanism that implements this mechanism we also derive sufficient conditions for the intermediary optimal mechanism to be implementable with revenue sharing contracts which are widely used in e business

pollution claim settlements under private information abstract the classical problem of resolving a nuisance dispute between a pollution generating firm and nearby residents is modelled here as a mechanism design problem we assume that the designer of the mechanism is the firm that it is uncertain about the actual losses suffered by residents and that the initial assignment of property rights is one where each resident is entitled to prevail we derive a profitmaximizing scheme under the individual rationality and incentive compatibility constraints and examine its properties it is shown that the outcomes it yields are sometimes inefficient moreover when many residents are affected by pollution and the degree of uncertainty with respect to the losses they suffer is large these inefficiencies become rampant

optimal contracts with public ex post information abstract we are concerned with the value of public ex post information about a seller s costs to an initially uninformed buyer we derive necessary and sufficient conditions for a public ex post signal s s that is correlated with the risk neutral seller s costs to render the initial information asymmetry inconsequential to the buyer the first best outcome for the buyer is shown to be feasible if 1 the dimension of s is at least that of or 2 the conditional likelihood function of s given is for one of its realizations sj a strictly increasing function of and more concave in than is the seller s cost function

targeting the poor using community information abstract governments and aid agencies target transfers to the poor but audits to deter the rich are costly this paper analyzes how community information can improve targeting if each community is given a hard budget constraint then targeting costs can be substantially reduced by asking recipients to make reports about each other audits are threatened in the event of a disagreement but never carried out in equilibrium this scheme is immune to collusion

bertrand competition for inputs and walrasian outcomes market making by merchants who obtain stock from suppliers and resell it to con sumers is modeled as a two stage pricing game with winner take all c ompetition for the inputs in contrast to fixed capacity models the re is a unique subgame perfect nash equilibrium spne which is walr asian for elastic demand and non walrasian for inelastic demand alte rnatively when merchants first sell forward contracts to consumers a nd then compete for supplies the unique spne is always walrasian th us the author has an equilibrium model in which walrasian price aris es not from the benevolent actions of a fictitious auctioneer but fr om optimal price setting behavior of merchants copyright 1988 by american economic association

chicken and egg competition among intermediation service providers we analyze a model of imperfect price competition between intermediation service providers we insist on features that are relevant for informational intermediation via the internet the presence of indirect network externalities the possibility of using the nonexclusive services of several intermediaries and the widespread practice of price discrimination based on users identity and on usage efficient market structures emerge in equilibrium as well as some specific form of inefficient structures intermediaries have incentives to propose non exclusive services as this moderates competition and allows them to exert market power we analyze in detail the pricing and business strategies followed by intermediation services providers copyright 2003 by the rand corporation

the use of village agents in rural credit delivery using a simple principal agent model this article examines the incentive problems that arise when a formal financial institution such as a rural bank utilises a member of the rural community to act as an agent in screening potential borrowers and collecting repayment optimal compensation schemes are derived for the agent and their implications are discussed in addition i show that the norms and rules that govern village life may aid the financial institution by helping to constrain possible strategic behaviour by the agent

cooperation among competitors some economics of payment card associations we analyze platforms in two sided markets with network externalities using the specific context of a payment card association we study the cooperative determination of the interchange fee by member banks the interchange fee is the access charge paid by the merchants banks the acquirers to cardholders banks the issuers we develop a framework in which banks and merchants may have market power and consumers and merchants decide rationally on whether to buy or accept a payment card after drawing the welfare implications of a cooperative determination of the interchange fee we describe in detail the factors affecting merchant resistance compare cooperative and for profit business models and make a first cut in the analysis of system competition

outreach sustainability and leverage in monitored and peer monitored lending abstract i study the contract design problem facing microfinance lending organizations mfos that want to maximize the impact and outreach of their lending activities to a target population of poor borrowers while remaining financially sustainable tradeoffs between outreach sustainability and financial leverage are shaped by the endogenous monitoring and delegation costs that arise within a chain of agency relationships subject to moral hazard between borrowers loan staff mfo equity owners and outside investors all else equal sustainable mfos that target poorer borrowers must charge higher interest rates have higher staff costs per dollar loaned and are less leveraged analysis of data for 72 mfos tends to support the findings

market making oligopoly this paper analyzes price competition between market makers who set costly capacity constraints before they intermediate between producers and consumers the unique equilibrium outcome with pure strategies at the capacity stage is the cournot outcome the paper thus provides a rationale for cournot type competition between market makers this contrasts with previous findings in the literature where due to the absence of capacity constraints that are set ex ante the bertrand result typically obtains

two sided markets a progress report the paper provides a road map to the burgeoning literature on two sided markets and presents new results it identifies two sided markets with markets in which the structure and not only the level of prices charged by platforms matters the failure of the coase theorem is necessary but not sufficient for two sidedness the paper builds a model integrating usage and membership externalities that unifies two hitherto disparate strands of the literature emphasizing either form of externality and obtains new results on the mix of membership and usage charges when price setting or bargaining determine payments between end users

optimal auction design in two sided markets a key feature of online markets for advertising e g sponsored links is that clicking rates depend on the searchers expectations that the platform selects relevant advertisers this article studies auction design by a platform that maximizes profits in the long run where clicking rates are mechanism dependent in line with the practice of the major search engines the revenue maximizing mechanism is a scoring auction that combines the willingness to pay and the relevance to searchers of advertisers by trading off rent extraction and clicking volume this mechanism works as a cross subsidization device between searchers and advertisers

repayment performance in group based credit programs in bangladesh an empirical analysis abstract this paper analyzes the repayment rates of 128 credit groups belonging to three group based credit programs in bangladesh the association for social advancement asa the bangladesh rural advancement committee brac and the rangpur dinajpur rural service rdrs using tobit analysis specific tests are performed on the following hypothesized determinants group size size of loans degree of loan rationing enterprise mix within groups demographic characteristics social ties and status and occurrence of idiosyncratic shocks the paper concludes that if basic principles of prudential banking are adhered to repayment rates can be good even in poor and remote communities the important thing for financial institutions is to tailor services such that it becomes worthwhile for the poor to establish a profitable long term association in addition more freedom to members in the process of group formation is recommended

asymmetric information bargaining problems with many agents a yes or no decision must be made about some issue all agents must agree the coase theorem asserts that the efficient outcome will always result suppose the value positive or negative that an individual attaches to an affirmative decision is privately known to that individual it is proved under very mild conditions that with independent types as the number of agents increases the probability of an affirmative efficient decision goes to zero an example in which it is common knowledge that an affirmative decision is efficient and yet the probability of such a decision goes to zero is given

efficient mechanisms for public goods with use exclusions constrained efficient provision of an excludable public good is studied in a model where preferences are private information the provision level is asymptotically deterministic making it possible to approximate the optimal mechanism with a mechanism that provides a fixed quantity of the good and charges fixed user fees for access in general the fixed fees involve third degree price discrimination but if names are uninformative about preferences the analysis provides a justification for average cost pricing copyright 2004 wiley blackwell

dominant strategy implementation of bayesian incentive compatible allocation rules abstract a large literature on incentive mechanisms represents incentive constraints by the requirement that truthful reporting be a bayesian equilibrium this paper identifies mechanism design problems for which there is no loss in replacing bayesian incentive compatibility by the stronger requirement of dominant strategies we identify contexts where it is possible to change the transfer payments of an optimal bayesian mechanism so as to create dominant strategies and yet leave every participant s expected utility unchanged we also address the issue of multiple equilibria and unique implementation contexts where these results apply include auctions bilateral bargaining procurement contracting and intrafirm resource allocation

designing credit agent incentives to prevent mission drift in pro poor microfinance institutions abstract credit agents in microfinance institutions mfis must be given incentives to acquire information on potential borrowers and select them in accordance with the mfi s objectives we show that while giving incentives has no cost in for profit mfis it is costly in pro poor mfis when repayment and wealth are positively correlated a pro poor mfi cannot obtain the selection of poor clients in the proportion it wishes with incentives based solely on repayment it then becomes necessary to audit the share of very poor borrowers selected by an agent in order to provide the latter with adequate incentives when audit costs are large pro poor mfis may have to forego selection on wealth and use other targeting devices such as working in impoverished geographical locations driven by donor concerns with mission drift away from the poor audits on the wealth status of clients have been introduced at the level of mfis we show that introducing pro poor incentives requires extending such audits to the level of credit agents

full extraction of the surplus in bayesian and dominant strategy auctions we consider auctions for a single indivisible object in the case where the bidders have information about each other which is not available to the seller we show that the seller can use this information to his own benefit and we completely characterize the environ ments in which a well chosen auction gives him the same expected payoff as that obtainable were he able to sell the object with full information about each bidder s willingness to pay we provide this characterization for auctions in which the bidders have dominant strate gies and for those where the relevant equilibrium concept is bayesian nash in both set ups the existence of these auctions hinges on the possibility of constructing lotteries with the correct properties we consider the situation in which an agent the seller possesses one indivisible unit of a good to which he attaches no value but the good has value to a number of potential buyers and its transfer to one of them would increase social welfare in particular the transfer to the buyer with the highest valuation maximizes social welfare in this paper we completely characterize environments in which the seller can design an auction that will enable him to capture for himself the full increase in social welfare induced by the transfer of the good to the bidder with the highest willingness to pay if the seller had full information about the reservation prices of potential buyers his optimal selling strategy would be very simple he would announce a price equal or very close to the highest reservation value the optimal strategy for the bidder with the highest evaluation would be to accept the offer note that we are treating a situation in which the seller can commit himself to a price as a result of the exchange the utility of the seller increases by the full amount of the increase in social welfare and he has been able to fully extract the surplus in many circumstances however a seller has only imperfect knowledge of the buyers willingnesses to pay in this case he must find some mechanism or auction which will enable him to maximize his benefit from the sale of the object the auction literature starts with this observation and shows how the seller can by an astute choice of auction extract the largest possible fraction of the surplus in general the literature has shown that this proportion is strictly less than one in some circumstances the bidders will have information about each other which is not available to the seller for instance in auctions for petroleum drilling rights bidders know the results of geological tests which they have

a general characterization of interim efficient mechanisms for independent linear environments we consider the class of bayesian environments with independent types and utility functions which are both quasi linear in a private good and linear in a one dimensional private value type parameter we call these independent linear environments for these environments we fully characterize interim efficient allocation rules which satisfy interim incentive compatibility and interim individual rationality constraints we also prove that they correspond to decision rules based on virtual surplus maximization together with the appropriate incentive taxes we illustrate these techniques with applications to auction design and public good provision

screening by the company you keep joint liability lending and the peer selection effect we look at an economic environment where borrowers have some information about the nature of each other s projects that lenders do not we show that joint liability lending contracts similar to those used by credit cooperatives and group lending schemes will induce endogenous peer selection in the formation of groups in a way that the instrument of joint liability can be used as a screening device to exploit this local information this can improve welfare and repayment rates if standard screening instruments such as collateral are unavailable

the efficiency of monetary exchange in search equilibrium search theoretic models of money emphasize monetary exchange as the outcome of economic environments characterized by bilateral trading frictions this paper analyzes the efficiency of monetary exchange in a search model of fiat money where individuals invest costly effort in the exchange process because the optimal effort each individual trader invests in exchange is based upon the private rather than social gains from trade decentralized monetary equilibria are shown to be inefficient relative to the social optimum however for an appropriate division of the gains from trade given to buyers and sellers it is possible to attain social efficiency the nature of these search externalities for monetary exchange and their implications for policy are evaluated and discussed copyright 1997 by ohio state university press