OLIGOPOLY AND COST SHARING IN ECONOMIES WITH PUBLIC GOODS

We study economies that involve both small and large traders as well as the choice of a public project. Within this framework, we establish two sufficient conditions under which the set of competitive allocations coincides with the core. Our first core equivalence result holds under the assumption that there is a countably infinite set of large traders similar to each other. The second result, independent of the number of large traders, requires the existence of a coalition of small traders with the same characteristics of the large traders. Finally, we show how the generalized Aubin approach to cooperation may dispense with both conditions.     

A remark on the equilibrium set of pureexchange economies

Summary.  We present a unified mathematical framework within which, among others, pure exchange economies with a finite set of agents, as well as those with a continuum of traders may be studied simultaneously. We prove that the reasoning presented by Balasko (1975) on the equilibrium set for finite economies generalizes very naturally to our setting. His results may therefore be recovered as a special case of those presented in this note. Received: April 9, 1996; revised version August 19, 1996     

The efficiency of competitive mechanisms under private information

We consider the efficiency properties of exchange economies where privately informed traders behave strategically. Specifically, a competitive mechanism is any mapping of traders’ reports about their types to an equilibrium price vector and allocation of the reported economy. In our model, some traders may have non-vanishing impact on prices and allocations regardless of the size of the economy. Although truthful reporting by all traders cannot be achieved, we show that, given any desired level of approximation, there is such that any Bayesian-Nash equilibrium of any competitive mechanism of any private information economy with or more traders leads, with high probability, to prices and allocations that are close to a competitive equilibrium of the true economy. In particular, allocations are approximately efficient. A key assumption is that there is small probability that traders behave non-strategically.     

Excess demand functions, equilibrium prices, and existence of equilibrium

Summary. For continuous aggregate excess demand functions of economies, the existing literature (e.g. Sonnenschein (1972, 1973), Mantel (1974), Debreu (1974), Mas-Colell (1977), etc.) achieves a complete characterization only when the functions are defined on special subsets of positive prices. In this paper, we allow the functions to be defined on a larger class of price sets, (allowing, for example the closed unit simplex, including its boundary). Besides characterizing excess demands for a larger class of economies, our extension provides a useful tool for proving other results. It allows us to characterize the equilibrium price set for a larger class of economies. It also permits extending Uzawa's observation (1962), by showing that Brouwer's Fixed-Point Theorem is implied by the Arrow-Debreu Equilibrium Existence Theorem (1954, Theorem I). Received: October 18, 1995; revised version June 28, 1996     

Advantageous monopolies

It is proved that in economies with one atom and one type of small traders, for each core allocation x there is a competitive allocation y whose utility to the monopolist is not greater than that of x, whenever either x is an equal treatment core allocation, or all small traders have the same homogeneous preferences. An example shows that these two requirements are, in general, indispensable for the result to hold.     

On the uniqueness of fully informative rational expectations equilibria

Summary. This paper analyzes two equivalent equilibrium notions under asymmetric information: risk neutral rational expectations equilibria (rn-REE), and common knowledge equilibria. We show that the set of fully informative rn-REE is a singleton, and we provide necessary and sufficient conditions for the existence of partially informative rn-REE. In a companion paper (DeMarzo and Skiadas (1996)) we show that equilibrium prices for the larger class of quasi-complete economies can be characterized as rn-REE. Examples of quasi-complete economies include the type of economies for which demand aggregation in the sense of Gorman is possible (with or without asymmetric information), the setting of the Milgrom and Stokey no-trade theorem, an economy giving rise to the CAPM with asymmetric information but no normality assumptions, the simple exponential-normal model of Grossman (1976), and a case of no aggregate endowment risk. In the common-knowledge context, we provide necessary and sufficient conditions for a common knowledge posterior estimate, given common priors, to coincide with the full communication posterior estimate. Received: May 29, 1997; revised version: July 18, 1997     

The problem of market size for Canadian cable television regulation

The policy of the Canadian radio television and telecommunications commission of awarding an exclusive right to provide cable television (CATV) service within a given licensed service area (LSA) rests partly on the presumption that CATV costs reflect economies of scale that are large relative to market size. Cost estimates from crosssections of CATV operations from 1985–1991 show increasing returns to scale and suggest that many LSAs were too small to capture these economies. The results also indicate that economies of scale for basic service declined over the 1980s and that the ‘natural monopoly’ characteristics of CATV may be eroded by further technological and regulatory changes.     

Endogenous market power

In this paper we develop a framework to study markets with heterogeneous atomic traders. The competitive model is augmented as we provide traders with correct beliefs about their price impacts to define equilibrium with endogenously determined market power and show that such equilibrium exists in economies with smooth utility and cost functions and is generically determinate. Traders? price impacts depend positively on the convexity of preferences or cost functions of the trading partners and are subject to mutual reinforcement. Compared to the competitive model, the volume of trade is reduced, and hence is Pareto inefficient. The price effects of non-competitive trading depend on the convexity of marginal utility or cost function.     

Optimal foreign trade for the price-insensitive soviet-type economy

For a centrally planned economy in which the planners do not substitute among goods, either in production or consumption, in response to changes in relative prices, the short-run offer curve is in general backward-bending, and the planners will be indifferent as to whether the country is “small” or “large” in world markets as long as it faces an elastic foreign offer curve. The Soviet Union is found to have a backward-sloping offer curve in trade with the Western market economies. This suggests that systematic Soviet manipulation of this trade in order to earn monopoly profits is unlikely.     

自然垄断的"三位一体"理论

传统自然垄断理论是建立在规模经济、范围经济和成本劣加性基础之上的，本文认为社会总价值或总效用和社会净收益的优加性是比成本劣加性更好地定义自然垄断的概念，并在对规模经济、范围经济和网络经济重新定义的基础上，从规模经济、范围经济、网络经济“三位一体”角度重新解释了自然垄断概念，提出了自然垄断的“三位一体”理论，为自然垄断产业规制及其改革奠定理论和实证基础。     

Edgeworth's conjecture with infinitely many commodities: commodity differentiation

Summary. Convergence of the cores of finite economies to the set of Walrasian allocations as the number of agents grows has long been taken as one of the basic tests of perfect competition. The present paper examines this test in the most natural model of commodity differentiation: the commodity space is the space of nonnegative measures, endowed with the topology of weak convergence. In Anderson and Zame [12], we gave counterexamples to core convergence in L ¹, a space in which core convergence holds for replica economies and core equivalence holds for continuum economies; in addition, we gave a core convergence theorem under the assumption that traders' utility functions exhibit uniformly vanishing marginal utility at infinity. In this paper, we provide two core convergence results for the commodity differentiation model. A key technical virtue of this space is that relatively large sets (in particular, closed norm-bounded sets) are compact. This permits us to invoke a version of the Shapley-Folkman Theorem for compact subsets of an infinite-dimensional space. We show that, for sufficiently large economies in which endowments come from a norm bounded set, preferences satisfy an equidesirability condition, and either (i) preferences exhibit uniformly bounded marginal rates of substitution or (ii) endowments come from an order-bounded set, core allocations can be approximately decentralized by prices. Received: July 29, 1996; revised version: January 14, 1997     

A qualitative approach to Markovian equilibrium in infinite horizon economies with capital

Using lattice programming and order theoretic fixpoint theory, we develop a new class of monotone iterative methods that provide a qualitative theory of Markovian equilibrium decision processes for a large class of infinite horizon economies with capital. The class of economies includes models with public policy, valued fiat money, monopolistic competition, production externalities, and various other nonconvexities in the production sets. The results can be adapted to construct symmetric Markov equilibrium in models with many agents and market incompleteness. As the methods are constructive, they provide the foundations for a rigorous analysis of numerical approximation schemes that study extremal Markovian equilibrium. Equilibrium comparative statics results relative to the space of economies are available. Of independent interest, we provide new conditions for preserving complementarity under maximization, and new generalized envelope theorems for nonconcave dynamic programming problems. Our fixed point algorithms are sharp, and are able to distinguish sufficient conditions under which Markovian equilibrium form a complete lattice of Lipschitz continuous, uniformly continuous and semicontinuous monotone functions as well as unique continuously differentiable equilibrium.     

The case against eliminating large denomination bills

When large denomination bills are preferred in illegal activities, what is the optimal policy response? We construct a dual currency model where illegal activity can be reduced by modifying the payment environment. In our model, legal (goods) traders are indifferent between small and large bills, but illegal (goods) traders face a lower transaction cost of using large bills in comparison to small bills because it is easier to conceal. We show that eliminating large bills can reduce illegal trade and its associated social cost. However, this pooling equilibrium is sub-optimal because the government can collect more seigniorage by allowing illegal traders to use large bills with a lower rate of return. When the transaction cost of using small bills for illegal traders is sufficiently large, a separating equilibrium, where legal traders use small bills and illegal traders use large bills, can maximize welfare by making an implicit transfer from the illegal traders to the legal traders.     

Convergence of the Aumann–Davis–Maschler and Geanakoplos bargaining sets

Summary. Geanakoplos [17] defined a notion of bargaining set, and proved that his bargaining set is approximately competitive in large finite transferable utility (TU) exchange economies with smooth preferences. Shapley and Shubik [26] showed that the Aumann–Davis–Maschler bargaining set is approximately competitive in replica sequences of TU exchange economies with smooth preferences. We extend Geanakoplos result to nontransferable utility (NTU) exchange economies without smooth preferences, and we extend the Shapley and Shubik result to non-replica sequences of NTU exchange economies with smooth preferences.Received: November 11, 1996This revised version was published online in February 2005 with corrections to the cover date.     

The Cost Structure of Australian Telecommunications

Since 1991 Australian telecommunications has undergone substantial reform. To a large extent, the economic correctness of pro-competitive policy depends on the non-existence of natural monopoly technology. This paper provides estimates of the Australian telecommunications system cost structure, and tests for subadditivity from 1943 to 1991. Additivity of the cost function after 1945 rejects the natural monopoly hypothesis and supports recent government policy. Diminished natural monopoly characteristics suggest that co-ordination between firms through networking can achieve similar economies as internal co-ordination within a monopoly. This finding is important, given the trend towards network unbundling, and service provision through interconnection.     

A testable model of consumption with externalities

This paper presents a nonparametric model of interdependent preferences, where an individual's consumption may act as an externality on the preferences of other consumers. We assume that individual price consumption data is observed for all consumers. It is known that the general consumption model with externalities imposes few restrictions on the observed data, where the consistency requirement is Nash rationalizability. We motivate potential games as an important sub class of games where the family of concave potential games is refutable and imposes stronger restrictions on observed data. We use this framework to extend the analysis of Brown and Matzkin [D. Brown, R. Matzkin, Testable restrictions on the equilibrium manifold, Econometrica 64 (1996) 1249-1262] on refutable pure exchange economies to pure exchange economies with externalities. Finally, we discuss an application of this model to inter-household consumption data.     

Structural change in the Australian electricity industry during the 1990s and the effect on household income distribution: A macro–micro approach

The Australian electricity industry experienced significant structural change during the 1990s mainly as a result of microeconomic reform. We analyse the effects of the structural change on the distribution of household income using a macro–micro approach. Our work shows that, nationwide, all income deciles experience higher real incomes in the order of 2%. Our results show that a previously state-owned monopoly industry can experience significant structural change while generating significant improvements in household real income without leading to significantly adverse impacts on national or regional income inequality. It suggests that policy makers in advanced economies should seriously consider such reforms given that they may generate large economic benefits with rather small economic costs.     

A pitchfork bifurcation in the tatonnement process★

Summary . This note extends the example of Gale (1963) by considering the continuous time tatonnement process for a class of two agent, two commodity exchange economies, parametrized by a number μ∈(0,1). We demonstrate that as the parameter passes a threshold value μ^* the unique, globally stable competitive equilibrium loses local stability while two new locally stable equilibria appear. Intuitively, as μ increases the income effect become increasingly more important relative to substitution effect, and eventually overwhelms the latter. As the parameter μ approaches 1, the economy tends to the example considered by Gale, as does the limiting behavior of the tatonnement. Received: February 28, 1996; revised version August 5, 1996     

Social welfare functions for economic environments with and without the pareto principle

It is shown for the case of private goods economies that every social welfare function satisfying a weak nonimposition condition and the independence of irrelevant alternatives axiom is of one of the following forms. It is either null, or the class of decisive coalitions is an ultrafilter, or the class of anti-decisive coalitions is an ultrafilter. In the case of a private goods economy with finitely many traders, the latter conditions imply the existence of either a dictator or anti-dictator. By requiring the Pareto principle as well, it is easily seen that the social welfare function must be dictatorial.     

Cost efficiency and scale economies in the Turkish insurance industry

This article examines the cost efficiency and scale economies of insurance firms in the Turkish insurance industry over a 15-year period, 1990–2004. Using the stochastic cost frontier model, cost efficiency scores and scale economies were estimated for each firm in the sample. The results show that mean cost inefficiencies range between 18.3 and 36.9% of total costs and they do not tend to decrease over time. On average, small firms are more cost efficient than large firms. Economies of scale appear present and significant for any class size. The results suggest that there is a substantial difference in scale economies between small and large insurance firms.