One important issue in mechanism design theory is to model agents’ behaviors under uncertainty. The classical approach assumes that agents hold commonly known probability assessments towards uncertainty, which has been challenged by economists in many fields. My thesis adopts alternative methods to model agents’ behaviors. The new findings contribute to understanding how the mechanism designer can benefit from agents’ uncertainty aversion and how she should respond to the lack of information on agents’ probability assessments. Chapter 1 of this thesis allows the mechanism designer to introduce ambiguity to the mechanism. Instead of informing agents of the precise payment rule that she commits to, the mechanism designer can tell agents multiple payment rules that she may have committed to. The multiple payment rules are called ambiguous transfers. As agents do not know which rule is chosen by the designer, they are assumed to make decisions based on the worst-case scenario. Under this assumption, this chapter characterizes when the mechanism designer can obtain the first-best outcomes by introducing ambiguous transfers. Compared to the standard approach where the payment rule is unambiguous, first-best mechanism design becomes possible under a broader information structure. Hence, there are cases when the mechanism designer can benefit from introducing ambiguity. Chapter 2 assumes that the mechanism designer does not know agents’ probability assessments about others’ private information. The mechanisms designed to implement the social choice function thus should not depend on the probability assessments, which are called robust mechanisms. Different from the existing robust mechanism design literature where agents are always assumed to act non-cooperatively, this chapter allows them to communicate and form coalitions. This chapter provides necessary and almost sufficient conditions for robustly implementing a social choice function as an equilibrium that is immune to all coalitional deviations. As there are social choice functions that are only implementable with coalitional structures, this chapter provides insights on when agents should be allowed to communicate. As an extension, when the mechanism designer has no information on which coalitions can be formed, this chapter also provides conditions for robust implementation under all coalition patterns. Chapter 3 assumes that agents are not probabilistic about others’ private information. Instead, when they hold ambiguous assessments about others’ information, they make decisions based on the worst-case belief. This chapter provides necessary and almost sufficient conditions on when a social choice goal is implementable under such a behavioral assumption. As there are social choice goals that are only implementable under ambiguous assessments, this chapter provides insights on what information structure is desirable to the mechanism designer.

Cette thèse porte sur les conséquences de l’aversion à l’ambiguïté dans des contextes dynamiques en économie. En particulier, elle s’intéresse aux conséquences de l’aversion à l’ambiguïté dans les décisions d’investissement irréversibles, ainsi que dans un problème d’aléa moral dynamique, modélisé en temps continu. Le premier chapitre propose une revue de la littérature traitant de l’aversion à l’ambiguïté en contexte dynamique. Nous y passons en revue les modèles existants ainsi que leurs applications en économie et en finance. Le second chapitre s’intéresse aux décisions d’investissement irréversible d’un monopole et de firmes en compétition parfaite, en présence d’ambiguïté à propos de la volatilité du processus stochastique gouvernant la demande. Cette notion particulière d’ambiguïté nécessite de mobiliser les outils récents de la théorie des espérances non linéaires. On y montre qu’en présence d’aversion à l’ambiguïté, la stratégie optimale d’un monopole implique d’investir plus rapidement que dans un marché en concurrence parfaite. Le troisième chapitre s’appuie sur les résultats du second chapitre pour traiter le cas d’une concurrence imparfaite entre deux firmes. Le quatrième chapitre traite d’un problème d’aléa moral dynamique en temps continu et on y introduit la notion plus classique d’ambiguïté à propos de la dérive du processus gouvernant l’incertitude. On y montre que sous certaines restrictions semblables au cas standard, le contrat optimal est linéaire par rapport à la production finale. Ce résultat nous permet ensuite de discuter l’effet de l’aversion à l’ambiguïté sur les incitations et l’utilisation de l’information. / This thesis focuses on the consequences of ambiguity aversion in dynamic contexts in economics. In particular, we focus on the consequences of ambiguity aversion in irreversible investment problems, and in dynamic moral hazard problems in continuous-time. The first chapter reviews the literature on ambiguity in dynamic contexts, and reviews existing models as well as their applications in economics and finance. The second chapter deals with irreversible investment in the monopoly case and under perfect competition, under ambiguous volatility. The notion of ambiguous volatility requires the use of recent tools in non linear expectation theory. We show that the optimal entry strategy of a monopoly under ambiguous volatility implies investing sooner than the perfectly competitive equilibrium under volatility ambiguity. The third chapter builds on the results of the second chapter and treats a special case of imperfect competition. The last chapter deals with a dynamic principal-agent problem under moral in continuous-time, in which agents perceive ambiguity about the drift of the relevant process. We show that under certain conditions, the optimal contract is linear in final output. We then use this result to discuss the effect of ambiguity aversion on the incentive power of the optimal contract and the informativeness principle.

This paper examines the optimal production and export decisions of an international firm facing exchange rate uncertainty when the firm's preferences exhibit smooth ambiguity aversion. Ambiguity is modeled by a second-order probability distribution that captures the firm's uncertainty about which of the subjective beliefs govern the exchange rate risk. Ambiguity preferences are modeled by the (second-order) expectation of a concave transformation of the (first-order) expected utility of profit conditional on each plausible subjective distribution of the exchange rate risk. Within this framework, we show that ambiguity has no impact on the firm's propensity to export to a foreign country. Ambiguity and ambiguity aversion, however, are shown to have adverse effect on the firm's incentive to export to the foreign country.

京都大学 / 0048 / 新制・課程博士 / 博士(経済学) / 甲第19953号 / 経博第540号 / 新制||経||279(附属図書館) / 33049 / 京都大学大学院経済学研究科経済学専攻 / (主査)教授 江上 雅彦, 教授 若井 克俊, 教授 原 千秋 / 学位規則第4条第1項該当 / Doctor of Economics / Kyoto University / DFAM

This thesis consists of three chapters and investigates the issues related to liquidity risk, credit market contagion, and corporate cash holdings. The first chapter is coauthored work with Professor Jay Sa-Aadu and Associate Professor Ashish Tiwari and is titled ‘Market Liquidity, Funding Liquidity, and Hedge Fund Performance.’ The second chapter is sole-authored and is titled ‘Credit Market Contagion and Liquidity Shocks.’ The third chapter is coauthored with Steven Savoy and titled ‘Ambiguity Aversion and Corporate Cash Holdings.’ The first chapter examines the interaction between hedge funds’ performance and their market liquidity risk and funding liquidity risk. Using a 2-state Markov regime switching model we identify regimes with low and high market-wide liquidity. While funds with high market liquidity risk exposures earn a premium in the high liquidity regime, this premium vanishes in the low liquidity states. Moreover, funding liquidity risk, measured by the sensitivity of a hedge fund’s return to the Treasury-Eurodollar (TED) spread, is an important determinant of fund performance. Hedge funds with high loadings on the TED spread underperform low-loading funds by about 0.49% (10.98%) annually in the high (low) liquidity regime, during 1994-2012. The second chapter provides evidence on credit market contagion using CDS index data and identifies the channels through which contagion propagates in credit markets. The results show that funding liquidity and market liquidity are significant channels of contagion during periods with widening credit spreads and adverse liquidity shocks. These results provide support for the theoretical model proposed by Brunnermeier and Pedersen (2009) according to which negative liquidity spirals can lead to contagion across various asset classes. Furthermore, during periods with tightening credit spreads and positive liquidity shocks, the results indicate that a prime broker index and a bank index are important channels contributing to co-movement in credit spreads. This suggests that financial intermediaries play an important role in spreading market rallies across credit markets. The third chapter investigates the link between investors’ ambiguity aversion and precautionary corporate cash holdings. Investors’ ambiguity aversion is measured by the proportion of individual investors in a firm’s investor base who are hypothesized to be more ambiguity averse compared to institutional investors. We show that the value of cash holdings is negatively associated with the extent of ambiguity aversion in a firm’s shareholder base for firms that are financially constrained. Our results also show that financially constrained firms with a higher proportion of ambiguity averse investors hold less cash. These results provide support for models in which ambiguity averse investors dislike the cash holdings of firms, that are held for precautionary reasons to fund long term projects, given that the returns on long term projects are ambiguous.

We examine risk taking when the bank's preferences exhibit smooth ambiguity aversion. Ambiguity is modeled by a second-order probability distribution that captures the bank's uncertainty about which of the subjective beliefs govern the financial asset return risk. Ambiguity preferences are modeled by the (second-order) expectation of a concave transformation of the (first-order) expected utility of profit conditional on each plausible subjective distribution of the return risk. Within this framework, the banking firm finds it less attractive to take risk in the presence than in the absence of ambiguity. This result extends to the case of greater ambiguity aversion. Given that the competitive bank's smooth ambiguity preferences exhibit non-increasing absolute ambiguity aversion, imposing a more stringent capital requirement to the bank reduces the optimal amount of loans, if the bank's coefficient of relative risk aversion does not exceed unity. Ambiguity and ambiguity aversion as such have adverse effect on the bank's risk taking.

No description available.

With the election of President Trump, climate deniers feel emboldened and moved from the fringes to the centre of global policy making. We study how an agnostic approach to policy, based on Pascal's wager and allowing for subjective prior probability beliefs about whether climate deniers are right, prices carbon. Using the DICE integrated assessment model, we find that assigning a 10% chance of climate deniers being correct lowers the global price on carbon in 2020 only marginally: from $21 to $19 per ton of carbon dioxide if policymakers apply "Nordhaus discounting" and from $91 to $84 per ton of carbon dioxide if they apply "Stern discounting". Agnostics' reflection of remaining scientific uncertainty leaves climate policy essentially unchanged. The robustness of an ambitious climate policy also follows from using the max-min or the min-max regret principle. Letting the coefficient of relative ambiguity aversion vary from zero, corresponding to expected utility analysis, to infinity, corresponding to the max-min principle, we show how policy makers deal with fundamental climate model uncertainty if they are prepared to assign prior probabilities to different views of the world being correct. Allowing for an ethical discount rate and a higher market discount rate and for a wide range of sensitivity exercises including damage uncertainty, we show that pricing carbon is the robust response under rising climate scepticism. / Series: Ecological Economic Papers

In this dissertation, I propose that, post-action, people tend to be more optimistic about outcomes when their actions were based on malleable (vague) information compared to when their actions were based on unmalleable (precise) information. However, pre-action, no such difference occurs. I term this inconsistency in optimism in the pre and post-action stage, the Information Malleability Effect (IME). These actions could include the choice of a product, drawing a ball from an urn, or consumption of a food item. Prior research on ambiguity aversion has reliably documented that people are generally averse to making decisions based on malleable information. On the other hand, research on situated optimism has demonstrated that people exhibit a high level of optimism for events they consider more desirable and they distort the available information to make the desirable events seem more likely to occur. I review these two streams of literature and show that although both literatures make predictions in either the pre or the post-action stage, neither of them alone can explain the IME. I propose a theoretical framework to explain the underlying cause of the IME that combines these two streams of literature and utilizes the motivated reasoning account. Based on this framework, I posit hypotheses that are tested across a series of experiments. Experiment 1a and 1b demonstrate the IME in a between and within participant design. Experiment 2 demonstrates that interpretational flexibility of malleable information results in positive outcomes appearing more plausible and negative outcomes less plausible compared to when information is unmalleable. Experiment 3 provides support for the proposed underlying process by priming accuracy and desired goals.

I consider continuous time asset pricing models with stochastic differential utility incorporating decision makers' concern with ambiguity on true probability measure. In order to identify and estimate key parameters in the models, I use a novel econometric methodology developed recently by Park (2008) for the statistical inference on continuous time conditional mean models. The methodology only imposes the condition that the pricing error is a continuous martingale to achieve identification, and obtain consistent and asymptotically normal estimates of the unknown parameters. Under a representative agent setting, I empirically evaluate alternative preference specifications including a multiple-prior recursive utility. My empirical findings are summarized as follows: Relative risk aversion is estimated around 1.5-5.5 with ambiguity aversion and 6-14 without ambiguity aversion. Related, the estimated ambiguity aversion is both economically and statistically significant and including the ambiguity aversion clearly lowers relative risk aversion. The elasticity of intertemporal substitution (EIS) is higher than 1, around 1.3-22 with ambiguity aversion, and quite high without ambiguity aversion. The identification of EIS appears to be fairly weak, as observed by many previous authors, though other aspects of my empirical results seem quite robust. Next, I develop an approach to test for martingale in a continuous time framework. The approach yields various test statistics that are consistent against a wide class of nonmartingale semimartingales. A novel aspect of my approach is to use a time change defined by the inverse of the quadratic variation of a semimartingale, which is to be tested for the martingale hypothesis. With the time change, a continuous semimartingale reduces to Brownian motion if and only if it is a continuous martingale. This follows immediately from the celebrated theorem by Dambis, Dubins and Schwarz. For the test of martingale, I may therefore see if the given process becomes Brownian motion after the time change. I use several existing tests for multivariate normality to test whether the time changed process is indeed Brownian motion. I provide asymptotic theories for my test statistics, on the assumption that the sampling interval decreases, as well as the time horizon expands. The stationarity of the underlying process is not assumed, so that my results are applicable also to nonstationary processes. A Monte-Carlo study shows that our tests perform very well for a wide range of realistic alternatives and have superior power than other discrete time tests.