Agreeing to disagree in a countable space of equiprobable states

An example is given in which agents agree to disagree, showing that Aumann's (1976) Agreement Theorem does not extend to a countable space of equiprobable states of nature. Even in this unorthodox setting, if the sets of the information partitions are intervals, an agreement theorem holds. A result that describes the margin for disagreement is also obtained.Agreeing to disagree, Interactive epistemology, Bounded rationality.

Past expectations as a determinant of equilibrium prices - hysteresis in a simple economy

We give an illustration of hysteresis (path-dependence) in a simple economy. In the presence of multiple possible equilibrium prices, we find that past expectations determine present prices. This phenomenon of path-dependence is robust under perturbations of the economy.Hysteresis, Path-dependence, Tatônnement, Equilibrium selection

Free daily newspapers: too many incentives to print?

We consider a model in which a free daily newspaper distributes news to readers and sells ad-space to advertisers, having private information about its readership. Depending on the type of readers in the market, the newspaper's may have a "plentiful and seeking" audience or a "lacking and avoiding" audience. We find that if the readers are plentiful and seeking, the newspaper prints an excessive number of copies. The rationale for this over-printing strategy lies on the newspaper's need to send a credible signal to the advertisers that there are plentiful and seeking readers in the market. When the readers are lacking and avoiding, the newspaper chooses the socially optimal tirage (does not try to cheat the advertisers).two-sided markets, asymmetric information, free press

Agreeing to Disagree with Multiple Priors

We present an extension of Aumann's Agreement Theorem to the case of multiple priors. If agents update all their priors, then, for the Agreement Theorem to hold, it is sufficient to assume that they have closed, connected and intersecting sets of priors. On the other hand, if agents select the priors to be updated according to the maximum likelihood criterion, then, under these same assumptions, agents may still agree to disagree. For the Agreement Theorem to hold, it is also necessary to assume that the maximum likelihood priors are commonly known and not disjoint. To show that these hypotheses are necessary, we give several examples in which agents agree to disagree.Agreeing to disagree, multiple priors, Aumann's Agreement Theorem

Costly horizontal differentiation

We study the effect of quadratic differentiation costs in the Hotelling model of endogenous product differentiation. The equilibrium location choices are found to depend on the magnitude of the differentiation costs (relatively to the transportation costs supported by consumers). When the differentiation costs are low, there is maximum differentiation. When they are intermediate, there is partial differentiation, with a degree of differentiation that decreases with the differentiation costs. When they are above a certain threshold, there is no equilibrium. In any case, the socially optimal degree of differentiation is always lower than the equilibrium level. We also study the case of collusion between firms. If firms can combine locations but not prices, they locate asymmetrically when differentiation costs are high and choose maximum differentiation when they are low. When collusion extends to price setting, there is partial differentiation.Costly product differentiation, Spatial competition, Hotelling model

Private Information: Similarity as Compatibility

We investigate the continuity of equilibrium in differential information economies with a finite number of agents. In this setting, agents can make contingent contracts based on events that are commonly observed. With private information modelled as finite partitions of a compact and metrizable space of states of nature, we introduce a topology on information that takes into account the compatibility of information fields in assessing similarity between private information fields. This topology allows us to establish upper semicontinuity of the private core correspondence.Differential Information Economy, Asymmetric Information, Radner Equilibrium, Private Core, Topologies on Information.

Existence and generic efficiency of equilibrium in two-period economies with private state-verification

Private state-verification is introduced in a two-period economy with spot markets in both periods and complete futures markets for contingent delivery in the second period. Existence of equilibrium is established, under standard assumptions. The equilibrium allocation is shown to be generically efficient if the number of states is not greater than the number of goods.General equilibrium, Differential information, Private state-verification, Two-period economies, Existence of equilibrium, Generic efficiency

Using Cost Observation to Regulate Bureaucratic Firms

We study regulation of a bureaucratic provider of a public good in the presence of moral hazard and adverse selection. By bureaucratic we mean that it values output in itself, and not only profit. Three different financing systems are studied - cost reimbursement, prospective payment, and the optimal contract. In all cases, the output level increases with the bureaucratic bias. We find that the optimal contract is linear in cost (fixed payment plus partial cost-reimbursement). A stronger preference for high output reduces the tendency of the firm to announce a high cost (adverse selection), allowing a more powered incentive scheme (a lower fraction of the costs is reimbursed), which alleviates the problem of moral hazard.Procurement, Regulation, Adverse selection, Moral hazard, Bureaucracy

General equilibrium with private state verification

We study general equilibrium with private and incomplete state verification. Trade is agreed ex ante, that is, before private information is received. It is useful to define a list of bundles as a derivative good that gives an agent the right to receive one of the bundles in the list. Enforceable trade agreements can be described by Pi-measurable plans of lists of bundles, instead of Pi-measurable plans of bundles as in Radner (1968). In equilibrium, the price of a list coincides with the price of the cheapest bundle in the list, and it is always the cheapest bundle of the list that is delivered. This property leads to a system of linear inequalities which are deliverability constraints on the choice set. We investigate existence of equilibrium in the case in which preferences are Pi-measurable. If there is a perfectly informed trader in the economy, existence of equilibrium is guaranteed.General equilibrium, Differential information, Verifiability, Uncertain delivery, Lists of bundles, Rational expectations