The overlapping expectations and the collective absence of arbitrage conditions introduced in the economic literature to insure existence of Pareto optima and equilibria when short-selling is allowed and investors hold a single belief about future returns, is reconsidered. Investors use measures...

This paper assesses the quantitative impact of ambiguity on the historically observed financial asset returns and prices. The single agent, in a dynamic exchange economy, treats the conditional uncertainty about the consumption and dividends next period as ambiguous. We calibrate the agent's...

We provide a generalization of Harsanyi (1955)'s aggregation theorem to the case of incomplete preferences at the individual and social level. Individuals and society have possibly incomplete expected utility preferences that are represented by sets of expected utility functions. Under Pareto...

Considering that a natural way of sharing risks in insurance companies is to require risk by risk Pareto optimality, we offer in case of strong risk aversion, a simple computable method for deriving all Pareto optima. More importantly all Individually Rational Pareto optima can be computed...

This paper elaborates an axiomatic treatment of the Subjective Expected Utility (SEU) model that dispenses with the assumption of an exogenous state space. Within a state-free description of uncertainty and alternatives, axioms for preferences are formulated and shown to characterize the...

This paper seeks to interpret observable behavior and departures from Savage's model of Subjective Expected Utility (SEU) in terms of knowledge and belief. It is shown that observable behavior displays sensitivity to ambiguity if and only if knowledge and belief disagree. In addition, such an...

Harsanyi's axiomatic justification of utilitarianism is extended to a framework with subjective and heterogenous priors. Contrary to the existing literature on aggregation of preferences under uncertainty, society is here allowed to formulate probability judgements, not on the actual state of...

We investigate the empirical relation between ambiguity aversion, risk aversion and portfolio choices. We match administrative panel data on portfolio choices with survey data on preferences over ambiguity and risk. We report three main findings. First, conditional on participation, ambiguity...