Contributions published at Financial Economics (Thorsten Hens)

In this paper we propose a new tâtonnement process of short-period equilibria with rational expectations: current period prices move proportionally to current period excess demand while future prices are formed according to the perfect foresight hypothesis. It is shown that this process is locally asymptotically stable if all goods are gross substitutes, or if the equilibrium has no trade. In general this process differs from a tâtonnement process in contingent contracts prices and from a tâtonnement in asset and spot market prices. It also differs from Hicks' and exceptional stability. In an intertemporal variant of Scarf's example on the instability of the Walrasian tâtonnement process it will be seen that the tâtonnement process we propose is more stable than any other process investigated so far.

The purpose of this note is to demonstrate that the commonly held belief that incomplete and perverse pass-through are incompatible with perfect competition is wrong! To this end, we consider two types of firms both operating in two countries. The demand sides of the markets of the two countries are separated and each type of firm produces its good in one of these countries. We study the effect of an exchange-rate change on the competitive equilibrium prices in each country. When producing for the foreign market causes the same costs as producing for the home market then the “law of one price” holds and an exchange-rate change is completely offset by price changes. Furthermore, when cost functions neither exhibit economies nor diseconomies of scope between producing for the home and producing for the foreign market then prices move in the “right” directions in response to an exchange-rate change. However, with general cost structures, even in this simple perfectly competitive model, “perverse” directions of price changes can result from an exchange-rate change.

The paper studies the role and the formulation of the survival assumption with incomplete markets. We are able to show the existence of a competitive equilibrium when the agents' endowments lie on the boundary of their consumption set. However, for this some additional assumptions with respect to the complete market case are needed. These are joint restrictions on the asset structure and the distribution of the endowments and preferences.

This paper is aimed at characterizing excess demand functions around noncritical spot price systems in two-period exchange economies with incomplete markets and real assets.

This article gives a preference-based characterization of subjective expected utility for the general equilibrium model with a finite number of states. The characterization follows Savage (1954) as closely as possible but has to abandon his axiom (P6), atomlessness of events, since this requires an infinite state space. To introduce continuity we replace (P6) with a continuity assumption on the set of consequences and assume the preferences are smooth. Then we apply Savage's sure-thing principle and his state-independence axiom to get an additively separable utility representation. Finally, to separate subjective probabilities from basic tastes, we apply a new axiom, which states that for each pair of states the marginal rate of substitution is constant along the certainty line.