Individually-rational collective choice

In this paper I consider the following problem: there is a collection of exogenously given socially feasible sets, and for each one of them, each one of a group of individuals chooses from an individually feasible set. The fact that the product of the individually feasible sets is larger than the socially feasible set notwithstanding, there arises no conflict between individuals. Assuming that individual preferences are random, I here characterize collective choices in terms of the way in which individual preferences must co-vary in order to explain them. I do this by combining standard revealed preference theory and its counterpart under random preferences. I also argue that there exist collective choices that cannot be rationalized, and hence that the individual rationality assumption can be refuted

Identification of individual demands from market data under uncertainty

We show that, even under incomplete markets, the equilibrium manifold identifies individual demands everywhere in their domains. Under partial observation of the manifold, we determine maximal subsets of the domains on which identification holds. For this, we assume conditions of smoothness, interiority and regularity. It is crucial that there be date-zero consumption. As a by-product, we develop some duality theory under incomplete markets

Identification of preferences from market data

We offer a new proof that the equilibrium manifold (under complete markets) identifies individual demands globally. Moreover, under observation of only a subset of the equilibrium manifold, we find domains on which aggregate and individual demands are identifiable. Our argument avoids the assumption of Balasko (2004) requiring the observation of the complete manifold

Bundling without price discrimination

This paper examines the optimal bundling strategies of a multiproduct monopoly in markets in which a seller cannot monitor and thereby restrict the purchases of buyers to a single bundle, while buyers have resale opportunities. In such markets, the standard mechanism through which bundling increases seller profits, based on price discrimination, is not feasible. The profit-maximizing bundling strategy is characterized, given the restrictions on pricing policies resulting from resale and a lack of monitoring. The welfare implications of optimal bundling are analyzed

The testable implications of competitive equilibrium in economies with externalities

Suppose that one has a data set consisting of prices and individual endowments for some economy. Brown and Matzkin (Econometrica 64:1249-1262, 1996) have shown that there are conditions that the data have to satisfy, if the observed prices are determined by the competitive equilibrium process, given the observed endowments, when there are no external effects in the economy's interactions. The results here show that the same conclusion does not apply, in general, if the economy exhibits externalities. On the other hand: (i) some restrictions exist if there exist at least two commodities on which the individuals' preferences are weakly separable; (ii) although extremely mild, restrictions exist too if one observed individual consumption for the economy that causes the external effects; and (iii) importantly, even if the previous two cases do not apply, restrictions exist when the externalities that exist are in the form of a public good

No-arbitrage, state prices and trade in thin financial markets

We examine how non-competitiveness in financial markets affects the choice of asset portfolios and the determination of equilibrium prices. In our model, potential arbitrage is conducted by a few highly specialized institutional investors who recognize and estimate the impact of their trades on financial prices. We apply a model of economic equilibrium, based on Weretka (http://www.ssc.wisc.edu/~mweretka/Research, 2007a), in which price effects are determined endogenously as part of the equilibrium concept. For the case in which markets allow for perfect insurance, we argue that the principle of no-arbitrage asset pricing is consistent with non-competitive behavior of the arbitragers and extend the fundamental theorem of asset pricing to the non-competitive setting

On the existence of equilibrium with incomplete markets and non-monotonic preferences

We provide a shorter proof than Geanakoplos and Polemarchakis (1986) of the existence of equilibrium in an incomplete financial market economy with numeraire assets, under the weak assumption that asset returns are non-negative. Furthermore, we relax the strict monotonicity assumption on preferences and as an application we prove the existence of equilibrium when agents may disagree on zero probability events but do not plan to go bankrupt in any state

Competition in financial innovation

This paper examines the incentives offered by frictionless markets for innovation of assetbacked securities. Assuming homogeneous preferences across investors with heterogeneous risk-sharing needs and allowing for short selling of securities, we characterize economies in which competition provides insufficient incentives to innovate so that, in equilibrium, asset markets are incomplete in all (pure strategy) equilibria—even when innovation is essentially costless. Thus, we provide an alternative to Allen and Gale’s (1991) classic foundation for endogenous market incompleteness