CONTINUOUS PREFERENCE ORDERINGS REPRESENTABLE BY UTILITY FUNCTIONS

This paper surveys the conditions under which it is possible to represent a continuous preference ordering using utility functions. We start with a historical perspective on the notions of utility and preferences, continue by defining the mathematical concepts employed in this literature, and then list several key contributions to the topic of representability. These contributions concern both the preference orderings and the spaces where they are defined. For any continuous preference ordering, we show the need for separability and the sufficiency of connectedness and separability, or second countability, of the space where it is defined. We emphasize the need for separability by showing that in any nonseparable metric space, there are continuous preference orderings without utility representation. However, by reinforcing connectedness, we show that countably boundedness of the preference ordering is a necessary and sufficient condition for the existence of a (continuous) utility representation. Finally, we discuss the special case of strictly monotonic preferences.     

Optimal lottery

This article proposes an equilibrium approach to lottery markets in which a firm designs an optimal lottery to rank-dependent expected utility (RDU) consumers. We show that a finite number of prizes cannot be optimal, unless implausible utility and probability weighting functions are assumed. We then investigate the conditions under which a probability density function can be optimal. With standard RDU preferences, this implies a discrete probability on the ticket price, and a continuous probability on prizes afterwards. Under some preferences consistent with experimental literature, the optimal lottery follows a power-law distribution, with a plausibly extremely high degree of prize skewness.     

Diversification preferences in the theory of choice

Diversification represents the idea of choosing variety over uniformity. Within the theory of choice, desirability of diversification is axiomatized as preference for a convex combination of choices that are equivalently ranked. This corresponds to the notion of risk aversion when one assumes the von Neumann–Morgenstern expected utility model, but the equivalence fails to hold in other models. This paper analyzes axiomatizations of the concept of diversification and their relationship to the related notions of risk aversion and convex preferences within different choice theoretic models. Implications of these notions on portfolio choice are discussed. We cover model-independent diversification preferences, preferences within models of choice under risk, including expected utility theory and the more general rank-dependent expected utility theory, as well as models of choice under uncertainty axiomatized via Choquet expected utility theory. Remarks on interpretations of diversification preferences within models of behavioral choice are given in the conclusion.     

On the computation of optimal monotone mean–variance portfolios via truncated quadratic utility

We report a surprising link between optimal portfolios generated by a special type of variational preferences called divergence preferences (see Maccheroni et al., 2006) and optimal portfolios generated by classical expected utility. As a special case, we connect optimization of truncated quadratic utility (see ?erný, 2003) to the optimal monotone mean–variance portfolios (see Maccheroni et al., 2009), thus simplifying the computation of the latter.     

Harsanyi’s theorem without the sure-thing principle: On the consistent aggregation of Monotonic Bernoullian and Archimedean preferences

This paper studies the extension of Harsanyi’s theorem (Harsanyi, 1955) in a framework involving uncertainty. It seeks to extend the aggregation result to a wide class of Monotonic Bernoullian and Archimedean preferences (Cerreia-Vioglio et al., 2011) that subsumes many models of choice under uncertainty proposed in the literature. An impossibility result is obtained, unless we are in the specific framework where all individuals and the social observer are subjective expected utility maximizers sharing the same beliefs. This implies that non-expected utility preferences cannot be aggregated consistently.     

Unique induced preference representations

Machina [Machina, M.J., 1984. Temporal risk and the nature of induced preferences. Journal of Economic Theory 33, 199–231] considers an individual who has to choose from a set of alternative temporal uncertain prospects, and must take an action before the uncertainty is resolved, seeking to maximize the expected value of an (action determined) von Neumann-Morgenstern utility index. It is natural to ask if the set of underlying von Neumann-Morgenstern utility indices can be uniquely recovered solely on the basis of the thus induced (ordinal) preferences over temporal prospects. Machina’s conclusion is that “ordinal preferences alone will not suffice.” However, we show that it is possible to recover the action–utility set inducing the preferences uniquely if we restrict attention to action–utility sets for which no two actions induce the same preference relation on the space of temporal prospects, no action is redundant, and no action leads to a risk free outcome.     

Are CEOs expected utility maximizers?

Are individuals expected utility maximizers? This question represents much more than academic curiosity. In a normative sense, at stake are the fundamental underpinnings of the bulk of the last half-century’s models of choice under uncertainty. From a positive perspective, the ubiquitous use of benefit-cost analysis across government agencies renders the expected utility maximization paradigm literally the only game in town. In this study, we advance the literature by exploring CEO’s preferences over small probability, high loss lotteries. Using undergraduate students as our experimental control group, we find that both our CEO and student subject pools exhibit frequent and large departures from expected utility theory. In addition, as the extreme payoffs become more likely CEOs exhibit greater aversion to risk. Our results suggest that use of the expected utility paradigm in decision making substantially underestimates society’s willingness to pay to reduce risk in small probability, high loss events.     

Informativeness of experiments for meu

The celebrated Blackwell’s theorem demonstrates the equivalence of a notion of statistical informativeness and economic valuableness for the class of preferences that are represented by the subjective expected utility. This note shows that this equivalence holds for a larger class of preferences, namely maxmin$maxmin$ expected utility.     

Continuous extension of preferences

We consider the problem of extending preferences from a subset of a commodity space to the entire space. It is a simple consequence of the Tietze extension theorem that continuous preferences can be extended if they are defined on closed subsets of a normal space and are representable by utility functions. We show the following: If the space is a non-separable metric space, then extension of preferences is not always possible. In fact for (path-connected) metric spaces, extension property, utility representation property, and separability are equivalent to each other.     

A von Neumann–Morgenstern representation result without weak continuity assumption

In the paradigm of von Neumann and Morgenstern (1947), a representation of affine preferences in terms of an expected utility can be obtained under the assumption of weak continuity. Since the weak topology is coarse, this requirement is a priori far from being negligible. In this work, we replace the assumption of weak continuity by monotonicity. More precisely, on the space of lotteries on an interval of the real line, it is shown that any affine preference order which is monotone with respect to the first stochastic order admits a representation in terms of an expected utility for some nondecreasing utility function. As a consequence, any affine preference order on the subset of lotteries with compact support, which is monotone with respect to the second stochastic order, can be represented in terms of an expected utility for some nondecreasing concave utility function. We also provide such representations for affine preference orders on the subset of those lotteries which fulfill some integrability conditions. The subtleties of the weak topology are illustrated by some examples.     

Construction of a continuous utility function for a class of preferences

We construct a continuous utility indicator for a subclass of continuous preference relations, including some with thick indifference classes, using a measure theoretic technique related to that of Neuefeind (1972). This indicator is not continuous on the full class of continuous preferences endowed with the closed convergence topology. It appears that no such indicator can be constructed, although Mas-Colell (1975) has established that one exists. A finer topology for preferences seems appropriate.     

Consistent choice under uncertainty

Suppose ex post preferences are defined upon prizes and ex ante preferences are defined upon lotteries. Then the consistent choice of decision rules reigns whenever ex post optimality is equivalent to ex ante optimality. This essay provides a necessary and sufficient condition for consistent choice in terms of revealed preferences. Indeed, ex ante revealed preferences must be induced from ex post revealed preferences in a manner which requires them to satisfy the independence axiom from expected utility theory.     

Rationalizing investors’ choices

Assuming that agents’ preferences satisfy first-order stochastic dominance, we show how the Expected Utility paradigm can rationalize all optimal investment choices: the optimal investment strategy in any behavioral law-invariant (state-independent) setting corresponds to the optimum for an expected utility maximizer with an explicitly derived concave non-decreasing utility function. This result enables us to infer the utility and risk aversion of agents from their investment choice in a non-parametric way. We relate the property of decreasing absolute risk aversion (DARA) to distributional properties of the terminal wealth and of the financial market. Specifically, we show that DARA is equivalent to a demand for a terminal wealth that has more spread than the opposite of the log pricing kernel at the investment horizon.     

Guessing the beliefs

A decision maker facing Knightian uncertainty is about to tell if he prefers an act X or Y. Two agents try to guess what he is going to do. All of them have preferences that achieve a separation of utility from beliefs. The only thing that the two agents do not know is the beliefs, so they evaluate them. We give a definition of “guessing better” and deal with its implications. We study particular cases as subjective expected utility and Choquet expected utility.     

Informativeness of experiments for MEU—A recursive definition

The well-known Blackwell theorem states the equivalence of statistical informativeness and economic valuableness. Çelen (2012) generalizes this theorem, which is well-known for subjective expected utility (seu), to maxmin expected utility (meu) preferences. We demonstrate that the underlying definition of the value of information used in Çelen (2012) is in contradiction with the principle of recursively defined utility. As a consequence, Çelen’s framework features dynamic inconsistency. Our main contribution consists in the definition of a value of information for meupreferences that is compatible with recursive utility and thus respects dynamic consistency.     

Dynamic asset allocation when bequests are luxury goods

Luxury bequests impart systematic effects of age to an investor's optimal allocation: the expected percentage allocation to equities rises throughout retirement. When bequests are luxuries the marginal utility of bequests declines more slowly than the marginal utility of consumption. This is essentially lower risk aversion. As a retiree approaches death, her expected remaining lifetime utility is increasingly composed of bequest utility, and thus generates progressively lower risk aversion. A retiree responds by increasingly favoring the higher-return risky asset. Compared to standard preferences, luxury bequests elevate a retiree's average exposure to the risky asset, but the difference is small in early retirement.     

Credit market segmentation,essentiality of commodities,and supermodularity

We consider incomplete market economies where agents are subject to price-dependent trading constraints compatible with credit market segmentation. Equilibrium existence is guaranteed when either commodities are essential, i.e, indifference curves through individuals’ endowments do not intersect the boundary of the consumption set, or utility functions are concave and supermodular. The smoothness of mappings representing preferences, financial promises, or trading constraints is not required. Hence, we may include in our framework economies where ambiguity is allowed and agents maximize the minimum expected utility over a set of priors, or where markets include non-recourse collateralized loans.     

Developments in non-expected utility theories: an empirical study of risk aversion

This paper investigates different developments in non-expected utility theories. Our focus is to study the agent’s attitude towards risk in a context of monetary gambles. Based on simulated data of the “Deal or No Deal” TV game show, we first compare the performance of the expected utility model versus a loss-aversion model. We find that the loss-aversion model has a better performance compared to the expected utility model. We then study the attitude towards risk according to two parameters: the relative risk aversion coefficient defined over the value function and the probability weighting coefficient proposed by the Cumulative Prospect Theory. We find evidence for probability weighting being undertaken by contestants reflecting less risk aversion over large stakes. We also explore the performance of two models of rank-dependant utility: the Quiggin (1982) and the power probability weighting models. We find that the probability weighting coefficient is still significant for both models. Finally, we integrate initial wealth into the contestants’ preferences function and we show that the initial wealth level affects the estimates of risk attitudes.     

Some results on the existence of utility functions on path connected spaces

This paper concerns the existence of utility representations for preferences defined on a path connected space X. This includes any convex set. A classical result of Eilenberg (1941) proves the existence of utility representations when the consumption set is connected and separable. In an infinite dimensional space the above result may not be useful, because we lack, in general, the separability of the space. The non-separable spaces L^∞ and ca(K) are typical examples in mathematical economics. In this paper we show that a continuous preference relation ≽, on X has a continuous utility representation if and only if it is countably bounded, i.e., there is some countable subset F of X such that for all x in X there exist y and z in F with y≽x≽z. An easy corollary states that any continuous preference which has a best and a worst point has a continuous representation. We also obtain a convex continuous preference on a Banach lattice that has not a utility representation, because it is not countably bounded.     

Expected utility without bounds—A simple proof

We provide a simple proof for the existence of an expected utility representation of a preference relation with an unbounded and continuous utility function.