Discriminating Between Models of Ambiguity Attitude: a Qualitative Test

During recent decades, many new models have emerged in pure and applied economic theory according to which agents’ choices may be sensitive to ambiguity in the uncertainty that faces them. The exchange between Epstein (2010) and Klibanoff et al. (2012) identified a notable behavioral issue that distinguishes sharply between two classes of models of ambiguity sensitivity that are importantly different. The two classes are exemplified by the α-maxmin expected utility (MEU) model and the smooth ambiguity model, respectively; and the issue is whether or not a desire to hedge independently resolving ambiguities contributes to an ambiguity-averse agent's preference for a randomized act. Building on this insight, we implement an experiment whose design provides a qualitative test that discriminates between the two classes of models. Among subjects identified as ambiguity sensitive, we find greater support for the class exemplified by the smooth ambiguity model; the relative support is stronger among subjects identified as ambiguity averse. This finding has implications for applications that rely on specific models of ambiguity preference.

AN ECONOMIC PREMIUM PRINCIPLE UNDER THE DUAL THEORY OF THE SMOOTH AMBIGUITY MODEL

This study considers a pure exchange economy with insurance against ambiguous loss. Ambiguity preferences are represented by the dual theory of the smooth ambiguity model from Iwaki and Osaki (2014). The economic premium principle of Bühlmann (1980, 1984) is extended to ambiguity. We also perform some comparative statics and present sufficient conditions under which an increase in ambiguity aversion increases insurance demand and insurance premiums. Contrary to the result in Tsanakas and Christofides (2006), the optimal demand for insurance is not always comonotonic, because our model permits an economy comprising both ambiguity averse and ambiguity loving agents.

Comparative Risk Aversion in the Presence of Ambiguity

This paper suggests a characterization of increases in risk aversion within the smooth ambiguity model by Klibanoff, Marinacci, and Mukerji (2005). I show that an increase in risk aversion is qualitatively different from that under expected utility, due to the incomplete separation between risk and ambiguity attitude. The analysis clarifies how ambiguity perception and attitude depend on risk aversion. (JEL D81)