Adrian Bruhin

Risk and Rationality: Uncovering Heterogeneity in Probability Distortion

It has long been recognized that there is considerable heterogeneity in individual risk taking behavior but little is known about the distribution of risk taking types. We present a parsimonious characterization of risk taking behavior by estimating a finite mixture regression model for three different experimental data sets, two Swiss and one Chinese, over a large number of real gains and losses. We find two distinct types of individuals: In all three data sets, the choices of roughly 80% of the subjects exhibit significant deviations from rational probability weighting consistent with prospect theory. 20% of the subjects weight probabilities linearly and behave essentially as expected value maximizers. Moreover, the individuals are assigned to one of these two groups with probabilities of close to one resulting in a low measure of entropy. The reliability and robustness of our classification suggest using a mix of preference theories in applied economic modeling.

Viewing the future through a warped lens: Why uncertainty generates hyperbolic discounting

A large body of experimental research has demonstrated that, on average, people violate the axioms of expected utility theory as well as of discounted utility theory. In particular, aggregate behavior is best characterized by probability distortions and hyperbolic discounting. But is it the same people who are prone to these behaviors? Based on an experiment with salient monetary incentives we demonstrate that there is a strong and significant relationship between greater departures from linear probability weighting and the degree of decreasing discount rates at the level of individual behavior. We argue that this relationship can be rationalized by the uncertainty inherent in any future event, linking discounting behavior directly to risk preferences. Consequently, decreasing discount rates may be generated by peoples proneness to probability distortions.

Uncertainty Breeds Decreasing Impatience: The Role of Risk Preferences in Time Discounting

Future events are uncertain by their very nature. Therefore, peoples risk preferences are likely to play a role in the valuation of allegedly guaranteed future outcomes. We show that future uncertainty conjointly with peoples proneness to nonlinear probability weighting generates a unifying framework for explaining many anomalies in intertemporal choice, such as hyperbolic discounting and subadditivity of discount factors. Moreover, our approach implies that higher uncertainty of future prospects increases the hyperbolicity of discount rates, suggesting that institutional deficiencies such as lack of contract enforcement, may be a source of hyperbolic discounting behavior. Based on an experiment with monetary incentives, we show that peoples risk taking behavior is indeed a significant determinant of their time discounting behavior: Greater departures from linear probability weighting predict a stronger decline in impatience on the level of individual behavior.

The risk elicitation puzzle

Evidence shows that people’s preference for risk changes considerably when measured using different methods, which led us to question whether the common practice of using a single behavioural elicitation method (EM) reflects a valid measure. The present study addresses this question by examining the across-methods consistency of observed risk preferences in 1,507 healthy participants using six EMs. Our analyses show that risk preferences are not consistent across methods when operationalized on an absolute scale, a rank scale or the level of model parameters of cumulative prospect theory. This is at least partly explained by the finding that participants do not consistently follow the same decision strategy across EMs. After controlling for methodological and human factors that may impede consistency, our results challenge the view that different EMs manage to stably capture risk preference. Instead, we interpret the results as suggesting that risk preferences may be constructed when they are elicited, and different cognitive processes can lead to varying preferences.Pedroni et al. show that risk preferences vary across behavioural elicitation methods, challenging the view that risk preferences can be consistently captured by a single method.

Call of duty: the effects of phone calls on blood donor motivation

Little is known about the long‐term effects of interventions aimed at increasing turnout among voluntary blood donors.

Detecting heterogeneous risk attitudes with mixed gambles

We propose a task for eliciting attitudes towards risk that is close to real world risky decisions which typically involve gains and losses. The task consists of accepting or rejecting gambles that provide a gain with probability p and a loss with probability 1 − p. We employ finite mixture models to uncover heterogeneity in risk preferences and find that (i) behavior is heterogeneous, with slightly less than one half of the subjects behaving as expected utility maximizers, (ii) for the others, reference-dependent models perform better than those where subjects derive utility from final outcomes, (iii) models with sign dependent decision weights perform better than those without, and (iv) there is no evidence for loss aversion. The procedure is sufficiently simple so that it can be easily used in field or lab experiments where risk elicitation is not the main experiment.