Decreasing absolute risk aversion and utility indices derived from cake-eating problems

This paper establishes the following characterization of decreasing absolute risk aversion (DARA) utility indices: J exhibits DARA if and only if it is the indirect function corresponding to an infinite horizon cake-eating problem for some nondecreasing and concave utility function of consumption. The characterization is applied to the analysis of resource extraction under uncertainty and to an inverse optimal problem.     

Monotone risk aversion

Summary. This paper defines decreasing absolute risk aversion in purely behavioral terms without any assumption of differentiability and shows that a strictly increasing and risk averse utility function with decreasing absolute risk aversion is necessarily differentiable with an absolutely continuous derivative. A risk averse utility function has decreasing absolute risk aversion if and only if it has a decreasing absolute risk aversion density, and if and only if the cumulative absolute risk aversion function is increasing and concave. This leads to a characterization of all such utility functions. Analogues of these results also hold for increasing absolute and for increasing and decreasing relative risk aversion.Received: 31 January 2003, Revised: 15 January 2004, JEL Classification Numbers: D81.The views, thoughts and opinions expressed in this paper are those of the author in his individual capacity and should not in any way be attributed to Morgan Stanley or to Lars Tyge Nielsen as a representative, officer, or employee of Morgan Stanley.     

Parametric characterizations of risk aversion and prudence

Summary. Our first main result says that whether one decision maker is more risk averse than another can be determined from their attitudes toward a given two-parameter family of risks. When all risks belong to this family, risk aversion can be compared even when initial wealth is random. Our second main result solves a long-standing problem in mean-variance analysis: what is the interpretation of the concavity of utility as a function of mean and variance? We show that in the case of normal distributions, this utility function is concave if and only if the agent has decreasing prudence. Received: July 29, 1996; revised: October 2, 1998     

Relative risk aversion, relative prudence and comparative statics under uncertainty: The case of (μ, σ)‐preferences

From the expected‐utility approach, relative risk aversion being smaller than one and relative prudence being smaller than two emerge as preference restrictions that fully determine the optimal responses of decisions under uncertainty to certain shifts in probability distributions. We characterize the magnitudes of relative risk aversion and relative prudence in terms of the two‐parameter, mean‐standard deviation approach. We demonstrate that this characterization is instrumental in obtaining comparative static results in the two‐parameter setting. We further relate our findings to the results in the expected‐utility framework.     

The role of risk aversion in public goods dilemmas with environmental uncertainty: an experimental analysis

The purpose of this study is to extend earlier research on environmental uncertainty in public goods dilemmas. The present paper reports the results of an experiment designed to examine the effect of risk aversion on public goods provision. A von Neumann–Morgenstern utility function with constant coefficient of relative risk aversion is used to investigate the impact of risk attitudes within a threshold public goods environment. The outcome of the threshold public goods experiment shows that subjects are indifferent to the changes in environmental conditions. Additionally, the analysis indicates that risk aversion is a significant determinant of voluntary public goods contribution level.     

实际汇率与就业--基于内生劳动力供给的跨期均衡分析

文章在个体跨期最优模型中引入内生劳动力供给,并同时假定对资本流动存在限制,以此来分析实际汇率变动对就业的影响。结果发现:只有当消费者对商品消费的相对风险规避程度比较大,即消费的跨期替代弹性比较小时,本币实际贬值才会促进就业的增加,反之贬值会使就业减少。考虑到中国当前的具体情况,消费者商品消费的相对风险规避程度会比较大,因而人民币实际贬值会有利于就业。对中国的实证分析支持了这一结论,且该实证分析通过了实际汇率的超外生性检验。鉴于从长期来看中国消费者的相对风险规避程度有下降的趋势,过分的依赖于低币值的汇率政策来解决失业问题是不可行的。     

Intertemporal elasticity of substitution and risk aversion: are they related empirically?

This article examines the relationship between two types of preference: preference of intertemporal choices and preference towards risk. In the simplest form of the constant relative risk aversion utility function, the intertemporal elasticity of substitution (IES) and risk aversion have an inverse relationship. However, there is no empirical evidence that suggests this inverse relationship holds. We examine the relationship between risk aversion and IES using household consumption data from the Consumer Expenditure Survey during 1996–2010. Multiple risk domains are selected to represent risk preference, and for each domain, we consider some households to be more risk averse than others. We separately estimate IES for the more risk-averse and less risk-averse households. We find that the IES estimates are generally smaller for the more risk-averse households than for the less risk-averse households and that the difference is statistically significant in the majority of the financial domains. This finding supports the inverse relationship between the two parameters, although considerable heterogeneity is found across domains.     

From sure to strong diversification

This paper presents a characterization of weak risk aversion in terms of preference for sure diversification. Similarly, we show that strong risk aversion can be characterized by weakening preference for diversification,as introduced by Dekel (Econometrica 57:163,1989), in what we call preference for strong diversification. We are grateful to Jean-Yves Jaffray, Peter Wakker and anonymous reference for very helpful suggestions and comments.     

Real estate and relative risk aversion with generalized recursive preferences

This paper investigates how real estate wealth affects the household’s attitude toward risk, and derives the closed-form expressions for risk aversion with generalized recursive preferences. We find three channels through which real estate wealth affects risk aversion, and these channels are absent in the traditional measure of relative risk aversion as in Arrow (1965) and Pratt (1964). First, illiquidity and fluctuations in real estate value increase consumption risk, thereby increasing risk aversion. Second, real estate as an asset provides a cushion for absorbing negative shocks to households, reducing risk aversion. Third, an increase in real estate prices lowers the profit of the firm that uses real estate as a factor of production, induces a decline in the real wage, and causes a rise in consumption risk. This channel increases risk aversion. We study how these channels as a whole determine relative risk aversion using a basic real business cycle model with generalized recursive preferences and compare the results with the case of expected utility preferences. Finally, we explore the implications of the firm’s and the household’s real estate holdings and illiquidity of real estate on the risk premiums for equity and real estate.     

Risk and risk aversion when states of nature matter

When uncertainty is associated with some intrinsically relevant states of nature, there is no reason for an agent to base his or her preferences only on probability distribution of claims. We propose a new concept of risk for state-contingent claims that, unlike the standard concept of Rothschild–Stiglitz, does not identify state-contingent claims with their probability distribution. This concept is called mean-independent risk, and we provide a simple characterization in terms of marginal utilities of (non-expected) utility functions that exhibit aversion to mean-independent risk. We study implications of aversion to mean-independent risk on agents’ choices under uncertainty. This research has been supported by the NSF under Grant SES-0099206. I have benefited from numerous conversations with Rose-Anne Dana and illuminating discussions with Tadeusz Miłosz about the theory of subgradients.     

Repetitive risk aversion

We propose a reasonable condition, which we call repetitive risk aversion (RRA), to be imposed on any utility function to account for the observed data on the relationship between the degree of absolute risk aversion and wealth. We deduce this condition from the concept of the fear of ruin (Aumann and Kurz 1977) and show it to be equivalent to the behaviorally meaningful condition that the risk premium is increasing at a non-increasing rate with the size of the bet. We drive mixed risk aversion, which is known to be stronger than standard and thus proper risk aversion, from RRA. We present several economic applications of RRA to demonstrate that it delivers better comparative static results.I am thankful to Jacques Drèze and Louis Eeckhoudt for their comments. I greatly appreciate the comments of an anonymous reviewer of this journal which have resulted in substantial improvement to both the content and presentation of the paper. An earlier version of this paper was presented at seminars at Brown, CORE, Hopkins, HKUST, Yale, and IMS     

Ambiguity Made Precise: A Comparative Foundation

The theory of subjective expected utility has been recently extended to allow ambiguity to matter for choice. We propose a notion of absolute ambiguity aversion by building on a notion of comparative ambiguity aversion. We characterize it for a preference model which encompasses some of the most popular models in the literature. We next build on these ideas to provide a definition of unambiguous act and event and show the characterization of the latter. As an illustration, we consider the classical Ellsberg 3-color urn problem and find that the notions developed in the paper provide intuitive answers. Journal of Economic Literature Classification Number: D81.     

Risk aversion in the Eurozone

We propose a New Keynesian Dynamic Stochastic General Equilibrium (DSGE) model where a risk aversion shock enters a separable utility function. We analyze five periods from 1971 through 2011, each lasting for 20 years, to follow over time the dynamics of several parameters such as the risk aversion parameter; the Taylor rule coefficients; and the role of the risk aversion shock in output, inflation, interest rate, and real money balances in the Eurozone. Our analysis suggests that risk aversion was a more important component of output and real money balance dynamics between 2006 and 2011 than it was between 1971 and 2006, at least in the short run.     

Endogenous fixprices and sticky price adjustment of risk-averse firms

A risk-averse price-setting firm which knows the quantity demanded at the status quo price but has imperfect information otherwise may choose not to change it although an otherwise identical risk-neutral firm would do so, provided the variance of the firm's subjective probability distribution over quantities demanded as a function of price displays a kink at the status quo. This is equivalent to risk aversion of order one. When no such endogenous fixprice exists, the size of price adjustment still tends to zero as risk aversion tends to infinity, and to any arbitrarily small menu cost there exists a degree of risk aversion so that the firm will not adjust.     

An experimental study of precautionary bidding

Auctions often involve goods exhibiting a common-knowledge ex-post risk. In such auctions, precautionary bidding predicts that under expected utility, DARA bidders reduce their bids by more than the appropriate risk premium. Because the degree of riskiness of an auctioned good and bidders׳ levels of risk aversion are difficult to observe in field settings, we conduct experimental auctions that allow us to identify the precautionary premium directly. We find strong evidence for precautionary bidding. The effect is robust to changes in experimental design features. Our experiment provides the first empirical demonstration of precautionary motives in a strategic setting.     

ON THE CONCAVITY AND QUASICONCAVITY PROPERTIES OF UTILITY FUNCTIONS

Concavity and quasiconcavity have always been important properties in financial economics particularly in decision problems when an objective function has to be maximized over a convex set. Both properties have mainly been used as purely technical assumptions. In this paper, we link concavity and quasiconcavity of a utility function to the basic concepts of risk aversion, prudence, risk vulnerability and temperance. We show that concavity means the agent is more risk vulnerable than prudent. In particular, we can see when a function is both concave and quasiconcave and when it is only quasiconcave.     

The role of transaction costs and risk aversion when selecting between one and two regimes for portfolio models

Estimation of the inputs is the main problem when applying portfolio analysis, and Markov regime-switching models have been shown to improve these estimates. We investigate whether the use of two-regime models remains superior across a range of values of risk aversion and transaction costs, in the presence of skewness and kurtosis and no short sales. Our results for US data suggest that, due to differences in their risk preferences and transactions costs, most retail investors may prefer to use one-regime models, while investment banks may prefer to use two-regime models.     

基于后悔规避的投资组合模型及其实证分析

由于人的情感、认知等因素对投资活动有直接影响,本文在投资活动中引入人的情感因素,提出了基于后悔规避的投资者效用函数,该效用函数是期末财富和预期财富的函数。建立了存在无风险资产时的最优投资组合模型,发现基于后悔规避投资组合模型的组合前沿存在两基金分离的现象。对我国上海股票市场进行了实证分析,得到了基于后悔规避投资组合模型的组合前沿,并验证了组合前沿存在两基金分离现象的结论。     

风险厌恶测定与我国银行治理效率的实证研究

基于FDIC对商业银行贷款损失所设定的概率分布,本文利用VaR方法对商业银行风险厌恶程度进行了测定,并利用我国上市银行2004～2008年间的财务数据对商业银行的风险厌恶程度进行了实证分析,结果表明商业银行的风险控制可以反映其风险厌恶程度,风险厌恶程度在风险控制中得到充分体现.银行的风险厌恶程度越高,净资产回报率越高.     

Risk aversion, wealth, and the DARA hypothesis: A new test

The Pratt-Arrow hypothesis of decreasing absolute risk aversion (DARA) is widely invoked in economic models of uncertainty but empirical tests, especially those using nonexperimental data, have yielded mixed results. This paper reexamines the DARA hypothesis using an expected utility model of life insurance demand and a 23-year sample of aggregate time series data from the U.S. After controlling for household size, age, income, loss probabilities, premium expenses, and inflation, the effect of wealth on insurance demand is found to be positive and statistically significant in linear and loglinear regressions, explaining more than 93 percent of the variation in coverage. Thus, in contrast to the prevailing theory, this empirical test presents evidence of increasing absolute risk aversion. This research was completed during a sabbatical at the University of Pennsylvania's Wharton School of Business. The financial support of the S. S. Huebner Foundation for Insurance Education is greatly appreciated. The author is also indebted to participants at the Forty-Second International Atlantic Economic Conference in Washington, D.C. for helpful comments. Any errors are the responsibility of the author.