Erratum to “Do pure indivisibilities prevent core equivalence? Core equivalence theorem in an atomless economy with purely indivisible commodities only” [J. Math. Econ. 41 (4–5) (2005) 571–601]

We consider a pure exchange economy with a continuum of agents and finitely many indivisible commodities. Every commodity can be consumed only in integer amounts. Thus, agents’ preferences are locally satiated and no commodity bundle has necessarily local cheaper points. We introduce a core which is an intermediate concept between the strong core and the weak core. In our economy, this core is the most natural concept in the sense that it coincides with the set of all exactly feasible Walras allocations.     

Core and competitive equilibria: An approach from discrete convex analysis

We extend the assignment market (Shapley and Shubik, 1972; Kaneko, 1976, 1982) by utilizing discrete convex analysis. We consider the market in which buyers and sellers trade indivisible commodities for money. Each buyer demands at most one unit of commodity. Each seller produces multiple units of several types of commodities. We make the quasi-linearity assumption on the sellers, but not on the buyers. We assume that the cost function of each seller is M^♮-convex, which is a concept in discrete convex analysis. We prove that the core and the competitive equilibria exist and coincide in our market model.     

Indivisible commodities and an equivalence theorem on the strong core

We consider a pure exchange economy with finitely many indivisible commodities that are available only in integer quantities. We prove that in such an economy with a sufficiently large number of agents, but finitely many agents, the strong core coincides with the set of expenditure-minimizing Walrasian allocations. Because of the indivisibility, the preference maximization does not imply the expenditure minimization. An expenditure-minimizing Walrasian equilibrium is a state where, under some price vector, all agents satisfy both the preference maximization and the expenditure minimization.     

Housing markets with indivisibilities

A model of a rental housing market in which houses are treated as indivisible commodities is presented. A recursive equation that determines a competitive equilibrium is provided, and it is argued that this competitive equilibrium is representative of the set of all competitive equilibria. Using this representative equilibrium, several propositions on comparative statics are considered that have to do with how the competitive rents change when certain parameters of the model change.     

Competitive equilibria in economies with multiple indivisible and multiple divisible commodities

In this paper we consider a general equilibrium model with a finite number of divisible and a finite number of indivisible commodities. In models with indivisibilities it is typically assumed that there is only one divisible good, which serves as money. The presence of money in the model is used to transfer the value of certain amounts of indivisible goods. For such economies with only one divisible commodity Danilov et al. showed the existence of a general equilibrium if the individual demands and supplies belong to a same class of discrete convexity. For economies with multiple divisible goods and money van der Laan et al. proved existence of a general equilibrium if the divisible goods are produced out of money using a linear production technology and no other producers are present in the model.     

Contract equilibria in a regulated rental housing market

Various contractual equilibrium concepts for a regulated rental housing market are studied in this paper. Regulation refers to rental contracts with institutionally prescribed structures and rental prices, a situation common for housing markets with restrictive rental protection legislation. Contracts can then be considered as indivisible commodities with certain unusual characteristics. Existence of equilibria of the various types is shown under rather weak assumptions.     

Non-linear leontief models in abstract spaces

This paper is to elaborate, using a functional analysis approach, the mathematical aspects of scale-dependent input-output models developed by Evans, Sandberg, Lahiri and Chander. All the basic results are established in abstract spaces of any dimension and in the case of existence theorems we do not require the continuity of the input function. A further generalization is made to a model with alternative processes. An application is also made to a model with indivisible commodities.     

Existence and description of housing market equilibrium

A rental housing market with finite numbers of non-identical consumers and indivisible housing units, each composed of a vector of attributes, is studied. A partial equilibrium, open city analysis is presented in which all other commodities are perfectly divisible and elastically supplied on national markets. Sufficient conditions for the existence of an equilibrium are rigorously established using a fixed point argument that is based on a bidding arrangement between agents. It is then shown that, although the set of equilibria is not a singleton, all equilibria are similar enough to ensure a strong resemblance between open and closed cities.     

Core equivalence and welfare properties without divisible goods

We study an economy where all goods entering preferences or production processes are indivisible. Fiat money not entering consumers’ preferences is an additional perfectly divisible parameter. We establish a First and Second Welfare Theorem and a core equivalence result for the rationing equilibrium concept introduced in Florig and Rivera (2005a). The rationing equilibrium can be considered as a natural extension of the Walrasian notion when all goods are indivisible at the individual level but perfectly divisible at the level of the entire economy.     

Weak versus strong domination in a market with indivisible goods

The core of a market in indivisible goods can be defined in terms of strong domination or weak domination. The core defined by strong domination is always non-empty, but may contain points which are unstable in a dynamic sense. However, it is shown that there are always stable points in the core, and a characterization is obtained. The core defined by weak domination is always non-empty when there is no indifference, and has no instability problems. In this case, the core coincides with the unique competitive allocation.     

Theorems on the core of an economy with infinitely many commodities and consumers

It is known that the classical theorems of Grodal [Grodal, B., 1972. A second remark on the core of an atomless economy. Econometrica 40, 581–583] and Schmeidler [Schmeidler, D., 1972. A remark on the core of an atomless economy. Econometrica 40, 579–580] on the veto power of small coalitions in finite dimensional, atomless economies can be extended (with some minor modifications) to include the case of countably many commodities. This paper presents a further extension of these results to include the case of uncountably many commodities. We also extend Vind’s [Vind, K., 1972. A third remark on the core of an atomless economy. Econometrica 40, 585–586] classical theorem on the veto power of big coalitions in finite dimensional, atomless economies to include the case of an arbitrary number of commodities. In another result, we show that in the coalitional economy defined by an atomless individualistic model, core–Walras equivalence holds even if the commodity space is non-separable. The above-mentioned results are also valid for a differential information economy with a finite state space. We also extend Kannai’s [Kannai, Y., 1970. Continuity properties of the core of a market. Econometrica 38, 791–815] theorem on the continuity of the core of a finite dimensional, large economy to include the case of an arbitrary number of commodities. All of our results are applications of a lemma, that we prove here, about the set of aggregate alternatives available to a coalition. Throughout the paper, the commodity space is assumed to be an ordered Banach space which has an interior point in its positive cone.     

A note on the strong core of a market with indivisible goods

This note proves that the strong core is included in the set of competitive allocations in the Shapley–Scarf market model with indivisible goods, and gives an example that the non-empty strong core is strictly included in the set of competitive allocations.     

Core equivalence with differentiated commodities

This paper presents improved core equivalence results for atomless economies with differentiated commodities in the framework of Ostroy and Zame (1994). Commodity bundles are elements of the space $M\left(K\right)$ of signed Borel measures on a compact space $K$ of commodity characteristics. Ostroy and Zame provide two sufficient conditions for core equivalence: It is sufficient that markets are “physically thick”, so that there are many suppliers of every commodity, or that markets are “economically thick”, so that consumers are sufficiently willing to substitute commodities with a similar composition for each other. The sufficient conditions in Ostroy and Zame (1994) all imply that there are “many more agents than commodities”, an idea of Aumann that was formalized and discussed in Tourky and Yannelis (2001) and Greinecker and Podczeck (2016). We generalize the framework in Ostroy and Zame (1994) and weaken their sufficient conditions to not imply the presence of “many more agents than commodities”. In particular, we drop the requirement that $K$ is metrizable from the basic model, the requirement of an uniform bound on endowments from the condition of “physically thick markets”, and the requirement that preferences are weak${}^1$-continuous from the condition of “economically thick markets”. Core equivalence still holds, showing that “many more agents than commodities” are not needed for core equivalence in models of commodity differentiation.     

The strong sequential core for two-period economies

The strong sequential core for two-stage economies with a possibly incomplete set of assets in period zero and trade in commodities in period one consists of those goods allocations that are in the classical core and moreover, after realization of the state of nature, in the core of the economy where executed asset contracts serve as initial endowments. The strong sequential core coincides with the classical core when all possible state-contingent contracts may serve as an asset. For finance economies it is shown that the strong sequential core is generically empty when there is an incomplete set of assets. Outside the setting of finance economies, we show that the strong sequential core can be empty even if there is a complete set of assets. If the set of constrained feasible allocations resulting from trading in assets, is enlarged to include also allocations outside the agents’ consumption sets, then a complete set of assets is sufficient for the equivalence of the resulting semi-strong sequential core and the classical core.     

The coordinate-wise core for multiple-type housing markets is second-best incentive compatible

We consider the generalization of Shapley and Scarf’s (1974) [Shapley, L., Scarf’s, H., 1974. On cores and indivisibility. Journal of Mathematical Economics 1, 23–37.] model of trading indivisible objects (houses) to so-called multiple-type housing markets. We show that the prominent solution for these markets, the coordinate-wise core rule, is second-best incentive compatible.     

Coalition production economies with divisible and indivisible inputs: Asymptotic results

This paper investigates the asymptotic characteristics of the relations between the Shapley value and the core of replicated production economies with divisible and indivisible inputs.     

Existence of a competitive equilibrium when all goods are indivisible

This paper investigates an economy where all consumption goods are indivisible at the individual level, but perfectly divisible at the overall level of the economy. In order to facilitate trading of goods, we introduce a perfectly divisible parameter that does not enter into consumer preferences — fiat money. When consumption goods are indivisible, a Walras equilibrium does not necessarily exist. We introduce the rationing equilibrium concept and prove its existence. Unlike the standard Arrow–Debreu model, fiat money can always have a strictly positive price at the rationing equilibrium. In our set up, if the initial endowment of fiat money is dispersed, then a rationing equilibrium is a Walras equilibrium. This result implies the existence of a dividend equilibrium or a Walras equilibrium with slack.     

Afriat’s theorem for indivisible goods

We identify a natural counterpart of the standard GARP for demand data in which goods are all indivisible. We show that the new axiom (DARP, for “discrete axiom of revealed preference”) is necessary and sufficient for the rationalization of the data by a well-behaved utility function. Our results complement the main finding of Polisson and Quah (2013), who rather minimally modify the original consumer problem with indivisible goods so that the standard GARP still applies.     

Preference revelation games and strong cores of allocation problems with indivisibilities

This note considers the equilibrium outcomes of the preference revelation games in the general model of indivisible good allocation introduced by [Sönmez, T., 1999. Strategy-proofness and essentially single-valued cores. Econometrica 67, 677–689]. We adopt the concepts of coalitional equilibria and cores which are both defined in terms of the weak deviation or blocking by a prescribed class of admissible coalitions. We prove that if the solution which induces preference revelation games is individually rational and Pareto optimal and the class of admissible coalitions is “monotonic,” then the set of coalitional equilibrium outcomes coincides with the core. And we point out that the preceding analysis in the context of marriage problems [Gale, D., Shapley, L., 1962. College admissions and the stability of marriage. American Mathematical Monthly 69, 9–15] is hardly extended to the general model.     

BRAND AGRICULTURE AND ECONOMIC GEOGRAPHY: WHEN ARE HIGHLY DIFFERENTIATED PRODUCTS SUSTAINABLE IN THE REMOTE PERIPHERY?

This paper presents a general equilibrium model of new economic geography, incorporating brand agriculture that produces differentiated agricultural products. Focusing on the core‐periphery space, we show that highly differentiated brand agriculture can be sustained in the periphery even when access to the core market is not particularly good. This result supports the promotion of innovative products in rural areas in order to avoid direct price competition in generic commodities markets under unfavorable conditions.