irreversible choice of uncertain technologies with network externalities in this article i explore the problem of sequential and irreversible technology choice in the presence of network externalities when the technologies stochastically evolve over time early potential users are shown to adopt an irreversible technology too early compared to the social optimum the effect of increasing the uncertainty of the technologies on an early potential user s decision is analyzed i find that the sponsor of new emerging technology might choose a research strategy that is too safe i also study the consequences of allowing side payments between generations of consumers and demonstrate that an ex post optimal standardization policy can impair ex ante social welfare

strategic buyers and exclusionary contracts this paper characterizes equilibrium exclusionary contracts between buyers an incumbent firm and a potential entrant when buyers can either vertically integrate or contract with the outside entrant in this setting exclusionary contracts are generally shown to be efficient and to deter inefficient entry that would otherwise occur with multiple unorganized buyers equilibrium contracts are shown to take a divide and conquer form and in some cases to deter some efficient entry in such cases efficient contracting can be restored by a policy that prohibits price discrimination and gives agents free reign to sign exclusionary agreements copyright 1994 by american economic association

collateral in credit rationing in markets with imperfect information note in their 1981 article joseph stiglitz and andrew weiss analyze adverse selection and incentive effects in the loan market the models considered are based on two crucial assumptions borrowers are subject to limited liability and lenders cannot distinguish borrowers projects of different risk stiglitz and weiss show that a bank that raises its interest rate may suffer adverse selection because only risky borrowers will be willing to borrow at the higher rate thus lenders may choose not to raise the interest rate to eliminate excess demand resulting in the possibility of a credit rationing equilibrium stiglitz and weiss also consider briefly the role of collateral in such credit rationing models they conclude that lenders may choose not to use collateral requirements as a rationing device an increase in collateral requirements like an increase in the interest rate potentially leads to a decrease in the lender s expected return on loans because of resulting adverse incentive and selection effects the purpose of this note is to further investigate the role of collateral in these models stiglitz and weiss discussion in section iii establishes that adverse selection effects can result from increases in collateral when borrowers are risk averse i will show by returning to a model they discussed earlier in section i that the adverse selection effects can also occur when borrowers are risk neutral stiglitz and weiss outline a model to consider the use of collateral as a rationing device section iii in that model all potential borrowers face the same array of risky projects each potential borrower chooses at most one of those projects to undertake the individuals are by assumption risk averse with decreasing absolute risk aversion and possess different amounts of initial wealth thus choice of project if any to undertake and the method of finance selffinance from initial wealth or loan finance will differ from one individual to the next stiglitz and weiss show that among those who undertake risky projects and who choose borrowing as the method of finance wealthier individuals undertake riskier projects an increase in collateral has two effects on the market for loans those individuals who remain in the market will choose to undertake less risky projects and those individuals who drop out of the market are less wealthy low risk borrowers if the second effect is sufficiently strong then increased collateral requirements will mean decreased expected returns for the lender thus a credit rationing equilibrium may occur since lenders may not choose to use collateral requirements or the interest rate to eliminate excess demand the adverse selection effect just described does not occur in this model if the individuals are risk neutral consequently the potential for a credit rationing equilibrium is limited to cases where borrowers are risk averse to see that increases in collateral requirements can also result in adverse selection if borrowers are risk neutral consider the model stiglitz and weiss used to analyze the adverse selection effects of increases in the interest rate section i pp 395 99 it differs from the section iii model discussed above in three ways first borrowers are risk neutral second all projects ar loan financed the analogy to the section iii model is that no individuals have sufficient wealth to self finance projects third in the section

contracts as a barrier to entry it is shown that an incumbent seller who faces a threat of entry into his or her market will sign long term contracts that prevent the entry of some lower cost producers even though they do not preclude entry completely moreover when a seller possesses superior information about the likelihood of entry it is shown that the length of the contract may act as a signal of the true probability of entry

dynamic processes of social and economic interactions on the persistence of inefficiencies an economy with a finite number of agents and a finite number of states is considered an exogenous institutional rule prescribes which moves from one state to another are feasible to each coalition at each time an agent is called to act with some exogenous probability and he chooses a coalition a feasible new state to move the economy to and side payments between the agents in the coalition the setup can be applied to various dynamic processes of social and economic interactions such as legislative bargaining coalition formation or exchange economies whenever agents are unable to write long term contracts but are otherwise unconstrained both in their ability to write arbitrary spot contracts and in their ability to collude there can be long run inefficiencies with cycles or inefficient steady states however when agents are sufficiently patient the initial state from which the process starts plays no role in the long run moreover when there exists an efficient state that is free of negat

product introduction with network externalities the authors study the introduction of a new product in a market with network externalities there is a common presumption that such markets exhibit excess inertia i e that they are biased toward existing products in contrast the authors provide conditions under which equilibrium involves insufficient friction i e a tendency to rush into new incompatible technologies they also analyze the firms incentives to make their products compatible and they show that the firm introducing the new technology is biased against compatibility copyright 1992 by blackwell publishing ltd

a theory of endogenous coalition structures consider an environment with widespread externalities and suppose that bind ing agreements can be written we study coalition formation in such a setting our analysis proceeds by defining on a partition function an extensive form bargaining game we establish the existence of a stationary subgame perfect equilibrium for such a game our main results are concerned with the characterization of equilib rium coalition structures we develop an algorithm that generates under certain conditions an equilibrium coalition structure our characterization results are especially sharp for symmetric partition functions in particular we provide a uniqueness theorem and apply our results to a cournot oligopoly journal of economic literature classification numbers c71 c72 c78 d62 q 1999 academic press

higher order expectations in asset pricing we examine formally keynes idea that higher order beliefs can drive a wedge between an asset price and its fundamental value based on expected future payoffs we call this the higher order wedge which depends on the difference between higher and first order expectations of future payoffs we analyze the determinants of this wedge and its impact on the equilibrium price in the context of a dynamic noisy rational expectations model we show that the wedge reduces asset price volatility and disconnects the price from the present value of future payoffs the impact of the higher order wedge on the equilibrium price can be quantitatively large

cyclical delay in bargaining with externalities externalities between buyers are shown to induce delays in negotiations between a seller and several buyers delays arise in a perfect and complete information setting with random matching even when there is no deadline while with a deadline we identify delays both for positive and negative externalities without a deadline we find that 1 when externalities are positive there exists no spne in pure strategies with bounded recall that exhibits delay 2 when externalities are negative it may happen that all spne with bounded recall have the property that long periods of waiting alternate with short periods of activity this is the cyclical delay phenomenon

contracts and externalities how things fall apart a single principal interacts with several agents offering them contracts the crucial assumption of this paper is that the outside option payoffs of the agents depend positively on how many uncontracted or free agents there are we study how such a principal unwelcome though he may be approaches the problem of contract provision to agents when coordination failure among the latter group is explicitly ruled out two variants are considered when the principal cannot re approach agents there is a unique equilibrium in which contract provision is split up into two phases in phase 1 simultaneousoffers at good though varying terms are made to a number of agents in phase 2 offers must be made sequentially and their values are discontinuously lower they are close to the very lowest of all the outside options when the principal can repeatedly approach the same agent there is a multiplicity of equilibria in some of these the agents have the power to force delay they can hold off the principal s overtures temporarily but they must succumb in finite time in both models despite beingable to coordinate their actions agents cannot resist an invasion by the principal and hold to their best payoff it is in this sense that things eventually fall apart

on money as a medium of exchange we analyze economies in which individuals specialize in consumption and production and meet randomly over time in a way that implies that trade must be bilateral and quid pro quo nash equilibria in trading strategies are characterized certain goods emerge endogenously as media of exchange or commodity money depending both on their intrinsic properties and on extrinsic beliefs there are also equilibria with genuine fiat currency circulating as the general medium of exchange we find that equilibria are not generally pareto optimal and that introducing fiat currency into a commodity money economy may unambiguously improve welfare velocity acceptability and liquidity are discussed

contracting with externalities the paper studies inefficiencies arising in contracting between one principal and n agents when the utility of each agent depends on all agents trades with the principal when the principal commits to a set of publicly observable bilateral contract offers the arising inefficiency is due entirely to the externalities imposed on non signers in contrast when the principal s offers are privately observed the distortion is due to the externalities given agents equilibrium trades comparison of the two externalities determines the relative efficiency of the two contracting regimes in both cases we show that when n is large each agent can be treated as non pivotal provided that appropriate continuity assumptions are satisfied we also study the case in which the principal can condition each agent s trade on other agents messages we characterize the set of such mechanisms in which each agent s participation is voluntary when the principal can commit to any such mechanism she implements the first best outcome while threatening each deviator with the harshest possible punishment however in the presence of noise that goes to zero slower than n goes to infinity in the limit we obtain a generally inefficient outcome in which each agent feels non pivotal

technology adoption in the presence of network externalities we analyze technology adoption in industries where network externalities are significant the pattern of adoption depends on whether technologies are sponsored a sponsor is an entity that has property rights to the technology and hence is willing to make investments to promote it key findings include the following 1 compatibility tends to be undersupplied by the market but excessive standardization can occur 2 in the absence of sponsors the technology superior today has a strategic advantage and is likely to dominate the market 3 when one of two rival technologies is sponsored that technology has a strategic advantage and may be adopted even if it is inferior 4 when two competing technologies both are sponsored the technology that will be superior tomorrow has a strategic advantage

contract renegotiation and coasian dynamics consider a long term relationship between a seller and a buyer whose valuation for a per period service or a durable good is private as trade progresses the valuation will be partially revealed and it may be impossible for the parties to commit ex ante not to take advantage of this we analyse this situation first by supposing that the parties can sign a sequence of short term contracts and secondly by supposing that they can sign a long term contract but cannot commit not to renegotiate it later we find a close relationship in the second case between the optimal long term contract and the non commitment outcome in the standard coasian durable good model our results also have implications for hidden information principal agent models

delay in multilateral bargaining under complete information abstract this paper analyzes a complete information infinite horizon multilateral bargaining model in which one player bargains with each of the other players one at a time and binding cash offer contracts are used to govern transactions under a weak stationarity condition on equilibrium strategies we characterize the set of equilibria for the game we show that when players are sufficiently patient significant delay in reaching agreements may emerge and this delay can become longer quickly as the number of involved parties rises indeed when the number of bargainers is large perpetual disagreement can occur in equilibrium journal of economic literature classification numbers c78 d23 d62

coordination and discrimination in contracting with externalities divide and conquer abstract the paper studies bilateral contracting between n agents and one principal whose trade with each agent generates externalities on other agents it examines the effects of prohibiting the principal from i coordinating agents on her preferred equilibrium and ii making different contracts available to different agents these effects depend on whether an agent is more or less eager to trade when others trade more the prohibitions reduce the aggregate trade in the former case and have little or no effect in the latter case the inefficiencies under different contracting regimes are linked to the sign of the relevant externalities and are shown to be typically reduced by both prohibitions

opportunism in multilateral vertical contracting nondiscrimination exclusivity and uniformity comment an input supplier selling to competing downstream firms would benefit from publicly committing at the outset to all contracts efficient commitment however would require complete contracts the authors study instead bilateral contracting without commitment regarding others terms each firm then fears that the supplier might opportunistically renegotiate another s contract to increase bilateral profit at the firm s expense the authors show that nondiscrimination clauses generally cannot curb such third party opportunism even with symmetric firms to reassure firms crude forms of commitment may be adopted this could explain the pervasiveness of exclusivity arrangements and the striking uniformity and intertemporal rigidity of franchise contracts copyright 1994 by american economic association

naked exclusion comment the ability of an incumbent firm to deter entry by writing exclusionary contracts with customers has been a subject of contention in the antitrust literature the courts concern with such exclusionary contracts has been challenged by those who argue that an incumbent faced with buyers whose interest is to promote entry and competition would have to pay buyers more for the inclusion of exclusionary provisions than it could possibly gain from exclusion in a provocative article eric b rasmusen et al 1991 henceforth rrw have argued that an incumbent may in fact be able to exclude rivals profitably using such contractual provisions because it can exploit buyers lack of coordination in essence if buyers expect other buyers to sign such provisions then they may see little reason not to do so themselves the rrw argument is potentially an important one because most alleged instances of entry deterrence through exclusionary contracts with customers occur in situations with multiple buyers unfortunately however rrw s two main results contain errors in this note we reconsider the rrw model providing correct characterizations of the likelihood and cost of exclusion for an incumbent firm our results indicate that while the intuition suggested by rrw is valid the equilibrium likelihood and cost of exclusion differ from what rrw derive moreover our analysis illuminates some further aspects of exclusionary contracting with multiple buyers among these issues we focus on how an incumbent can use discriminatory offers to exploit the externalities that exist among buyers in the provision of competition in section i we review the basic assumptions of the rrw model in sections ii and iii we then consider in turn the cases of simultaneous and sequential offers studied by rrw for the simultaneous model we distinguish between settings in which the incumbent can and cannot discriminate in its offers to different buyers this distinction is the source of the problem in rrw s analysis their simultaneous offer model assumes no discrimination but the proof of their proposition 2 assumes at times that discrimination is feasible we show that absent the ability to discriminate the incumbent can exclude profitably only when buyers fail to coordinate on their most preferred continuation equilibrium in contrast we show that when discrimination is possible the incumbent need not rely on a lack of buyer coordination to segal department of economics landau building stanford university stanford ca 94305 e mail ilya segal stanford edu whinston department of economics northwestern university 2003 sheridan road evanston il 60208 e mail mwhinston nwu edu we thank eric rasmusen john wiley and participants in the berkeley stanford iofest the university of copenhagen vertical restraints conference and a seminar at the antitrust division of the u s department of justice for helpful comments we thank federico echenique for excellent research assistance 1 for example a recent department of justice investigation concerned the use of exclusive contracts by the leading provider of computerized ticketing services ticketmaster most major cities have several large concert sports venues in many cities ticketmaster has exclusive contracts with a very large share of these venues 2 the other leading response to the argument that contracts with buyers cannot be a profitable method of exclusion is given in philippe aghion and patrick bolton 1987 section i one factor limiting the applicability of the aghion and bolton theory however is that it involves partial exclusion the contracts signed are not fully exclusionary they involve finite stipulated damages and the profitability of the strategy arises from extracting rents from an entrant when entry occurs indeed in the aghion and bolton model contracts that fully exclude offer no benefits over writing no contract at all in section iii of their paper aghion and bolton also discuss a two buyer version of their model in which externalities arise across buyers in contrast to the analysis here and in rrw they allow the incumbent to make an offer to a buyer i that is conditional on the acceptance decision of the other buyer 3 r innes and r j sexton 1994 also discuss the use of discriminatory offers in the context of a model in which buyers can form coalitions with the entrant

cheap talk coordination and entry we show how costless nonbinding nonverifiable communication cheap talk can achieve partial coordination among potential entrants into a natural monopoly industry where the payoffs are qualitatively like the battle of the sexes the analysis would apply equally in other economic situations with such payoffs for example bargaining under complete information or choosing compatibility standards while cheap talk helps achieve asymmetric coordination in a symmetric mixed strategy equilibrium it cannot achieve complete coordination if the game involves even a small amount of conflict

a model of imperfect competition with keynesian features the recent literature on the reappraisal of keynes has viewed keynesian equilibria as arising when prices are fixed and effective demands and supplies are equilibrated through the adjustment of quantities one problem with this approach is that it lacks a theory of price determination in particular of why prices are fixed in the present paper we show that a number of keynesian features arise in a model in which prices are fully flexible but where agents have some monopoly power one advantage of this approach is that it provides a theory of the determination of both prices and quantities

negative externalities may cause delay in negotiation we study the strategic equilibria of a negotiation game where potential buyers are affected by identity dependent negative externalities the unique equilibrium of long finitely repeated generic games can either display delay where a transaction can take place only in several stages before the deadline or in spite of the random element in the game a well defined buyer exists that obtains the object with probability close to one

how to license intangible property we examine the optimal licensing strategy of a research lab selling to firms who are product market competitors we consider an independent lab as well as a research joint venture we show that 1 demands are interdependent and hence the standard price mechanism is not the profit maximizing licensing strategy 2 the seller s incentives to develop the innovation may be excessive 3 the seller s incentives to disseminate the innovation typically are too low 4 larger ventures are less likely to develop the innovation and more likely to restrict its dissemination in those cases where development occurs and 5 a downstream firm that is not a member of the research venture is worse off as a result of the innovation

network competition i overview and nondiscriminatory pricing we develop a model of unregulated competition between interconnected networks and analyze the mature and transition phases of the industry in this deregulated environ ment networks pay negotiated or regulated access charges to each other and com pete in prices for customers we show that a competitive equilibrium may fail to exist for large access charges or for large network substitutability and that freely negotiated access charges may prevent effective competition in the mature phase of the industry and erect barriers to entry in the transition toward competition last we examine the meaning and impact of policies such as the efficient component pricing rule

adoption externalities as public goods abstract a public good problem arises naturally in situations characterized by positive externalities or negative externalities for positive externalities agents furnish a public good by taking an action similarly for negative externalities agents furnish a public good by not taking an action we examine these externalities in a binary choice problem i e adoption externalities in each case there is a potential role for government intervention even when equilibrium transfers are not allowed since one equilibrium pareto dominates all others we analyze the positive and normative features of equilibria in these models and we explore the possibility of useful government intervention

the neo luddite s lament excessive upgrades in the software industry we examine two reasons why a monopoly supplier of software may introduce more upgrades than is socially optimal when the upgrade is backward but not forward compatible so users who upgrade reduce others network benefits one explanation involves a commitment problem profits and social welfare may suffer because ex post the monopolist will want to sell the upgraded product to new consumers the second involves consumer heterogeneity here oversupply arises from the difference between the externality that upgrades impose on the marginal and average consumer and from the effect of upgrades on sales of the base good