Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jmateco.2018.11.001

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

The objective of this study is to design a laboratory experiment to explore the effect of ambiguity on a subject's search behavior in a finite-horizon sequential search model. In so doing, we employ a strategy to observe the potential trend of reservation points that is usually unobserved. We observe that subjects behaving consistently across treatments reduce their reservation points in the face of ambiguity over point distribution. Our result is consistent with the theoretical implication obtained by Nishimura and Ozaki (J Econ Theory 119:299-333, 2004).

DOI： 10.1007/s11238-015-9488-x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：J C B MOHR  

Using a simple framework due to Cooper and John (1988) and Cooper (1999), this paper derives the conditions under which overconfidence and underconfidence of agents lead to Pareto improvement. We show that an agent's overconfidence in a game exhibiting strategic complementarity and positive spillovers and an agent's underconfidence in a game exhibiting strategic complementarity and negative spillovers can lead to Pareto improvement.

DOI： 10.1628/093245615X14273596659161

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

This paper proposes a class of independence axioms for simple acts. By introducing the -cominimum independence axiom that is stronger than the comonotonic independence axiom but weaker than the independence axiom, we provide a new axiomatization theorem of simple acts within the framework of Choquet expected utility. Furthermore, in order to provide the axiomatization of simple acts, we generalize Kajii et al. (J Math Econ 43:218-230, 2007) into an infinite state space. Our axiomatization theorem relates Choquet expected utility to multi-prior expected utility through the core of a capacity that is explicitly derived within our framework. Our result in this paper also derives Gilboa (Econometrica 57:1153-1169, 1989), Eichberger and Kelsey (Theory Decis 46:107-140, 1999), and Rohde (Soc Choice Welf 34:537-547, 2010) as a corollary.

DOI： 10.1007/s11238-013-9411-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CAMBRIDGE UNIV PRESS  

In this paper, we develop a simple two-period model of natural capital investment under Knightian uncertainty and analyze the effects of changes in the degree of ambiguity on the optimal natural capital investment. We find that the degree of Knightian uncertainty affects a government's natural capital investment. Moreover, we find that the direction of the effect of the Knightian uncertainty depends on the nature of uncertainty, that is, on whether the uncertainty is about the future level of natural capital or about the return from saving.

DOI： 10.1017/S1355770X13000661

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

The purpose of this paper is twofold. First, we generalize Kajii et al. (J Math Econ 43:218-230, 2007) and provide a condition under which for a game , its Mobius inverse is equal to zero within the framework of the -modularity of for . This condition is more general than that in Kajii et al. (J Math Econ 43:218-230, 2007). Second, we provide a condition under which for a game , its Mobius inverse takes non-negative values, and not just zero. This paper relates the study of totally monotone games to that of -monotone games. Furthermore, this paper shows that the modularity of a game is related to -additive capacities proposed by Grabisch (Fuzzy Sets Syst 92:167-189, 1997). To illustrate its application in the field of economics, we use these results to characterize a Gini index representation of Ben-Porath and Gilboa (J Econ Theory 64:443-467, 1994). Our results can also be applied to potential functions proposed by Hart and Mas-Colell (Econometrica 57:589-614, 1989) and further analyzed by Ui et al. (Math Methods Oper Res 74:427-443, 2011).

DOI： 10.1007/s00186-014-0468-7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

This paper analyzes the situation in which a national government introduces environmental regulations. Within the framework of an international duopoly with environmental regulations, an environmental tax imposed by the government in the home country can induce a foreign firm with advanced abatement technology to license it to a domestic firm without this technology. Furthermore, when the domestic firm's production technology is less efficient than that of the foreign firm, the foreign firm may freely reveal its technology to the domestic firm. These improvements through the voluntary transfer of technology imply that environmental regulations have positive impacts on innovation.
Resume Reglementation environnementale et transferts de technologie. Ce texte analyse le cas d'un gouvernement national qui etablit des reglementations environnementales. Dans le cadre d'un duopole international avec reglementations environnementales, le gouvernement national impose une taxe environnementale au plan domestique qui peut induire une firme etrangere qui dispose d'une technologie avancee qui reduit l'impact environnemental a vendre une licence permettant d'utiliser cette technologie a une firme domestique qui ne l'a pas. De plus, quand la technologie de production de la firme domestique est moins efficace que celle de la firme etrangere, la firme etrangere peut reveler sa technologie a la firme domestique. Ces ameliorations a travers les transferts volontaires de technologie impliquent que les reglementations environnementales ont des impacts positifs sur l'innovation.

DOI： 10.1111/caje.12100

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

In stock markets, we often observe portfolio inertia, i.e., a situation in which some stocks are not traded or not priced for a few minutes or longer. This is neither an exceptional situation in which some stock price soars too high to be priced, nor the one where some stock price plummets too much to be traded. By introducing the concept of Knightian uncertainty, Dow and Werlang (1992) account for the existence of portfolio inertia, which has not been accounted for under the concept of risk. This paper provides a characterization of the spread between buying and selling prices based on a parameter proposed by Ozaki and Streufert (1999, 2001) that enables us to estimate the attitude towards Knightian uncertainty, and shows that an increase (a decrease) in Knightian uncertainty expands (shrinks) the interval in which an investor never changes her initial position. Furthermore, we analyse the effect of an increase in Knightian uncertainty on portfolio inertia based on Epsilon-contaminations.

DOI： 10.1111/j.1467-8586.2010.00366.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

This paper examines the dynamic property of a macroeconomic model developed by Matsuyama [Am. Econ. Rev. 97(2007), pp. 503-516] in detail. It is shown that the model can be transformed into a version of the neuron model analysed by Hata [J. Math. Kyoto Univ. 22(1982), pp. 155-173, Chaos in Neural Network Models (in Japanese), Asakura, Tokyo 1998] and that the system can exhibit either periodic fluctuations or non-periodic (chaotic) fluctuations.

DOI： 10.1080/10236198.2011.601301

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

This paper analyzes a simple vertical product differentiation model with demand uncertainty and derives a risk neutral monopolist's optimal market entry timing, her optimal pricing and optimal quality choice by incorporating Knightian uncertainty, irreversibility, and flexibility in quality-enhancing investment into a continuous-time stochastic model. It is shown that an increase in Knightian uncertainty induces decreases in the optimal price, the optimal quality, and the value of undertaking the quality-enhancing investment by the monopolist. The social optimal entry timing, pricing and quality are also analyzed. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ijindorg.2011.04.002

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Extending the Grossman (J Polit Econ 80:223-255, 1972) model of health capital into a stochastic one, we analyze how the presence of Knightian uncertainty about the efficacy of health care affects the optimal health investment behavior of individuals. Using Gilboa and Schmeidler's (J Math Econ 18:141-153, 1989) model of maxmin expected utility (MMEU) with multiple priors, we show that an agent retains the initial level of health capital if the price of health care lies within a certain range. We also show that the no-investment range expands as the degree of Knightian uncertainty rises.

DOI： 10.1007/s10198-010-0238-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

I consider a problem in environmental policy design in which I focus on stock pollutants. In particular, I consider stock pollutants that cause severe damage on the environment and do not depreciate at all once they are released into the atmosphere and the ocean. The purposes of this paper are: (1) to provide an economic foundation for environmental policies based on the precautionary principle and the 1992 Rio Declaration on Environment and Development, and (2) to show that this optimal timing rule has a reservation property. Furthermore, I analyze the effect of an increase in ambiguity on the optimal timing of adopting some environmental policy, and show that an increase in ambiguity decreases the optimal timing of adopting the environmental policy.

DOI： 10.1007/s10640-010-9370-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：LOUISIANA STATE UNIV PR  

We analyze the optimal timing of an irreversible foreign direct investment by a foreign firm and the optimal tax policy by a host country under ambiguity, We derive the optimal GDP level at which the foreign firm switches from exporting to a foreign direct investment. Furthermore, we derive the optimal tax policy by the host country, and analyze the effect of an increase in ambiguity on the optimal tax policy. We show that the host country should reduce the optimal corporate tax rate from the host government's perspective in response to an increase in ambiguity. Our result is different from the one obtained by Pennings (2005) that shows that an increase in risk induces an increase in the optimal Corporate tax Fate. (C) 2009 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jmacro.2009.12.006

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

This article analyzes investors' portfolio selection problems in a two-period dynamic model of Knightian uncertainty. We account for the existence of portfolio inertia in this two-period framework. Furthermore, by incorporating investors' updating behavior, we analyze how observing new information in the first period will affect investors' behavior. By this analysis, we show that observing new information in the first period will expand portfolio inertia in the second period compared with the case in which observing new information has not been gained in the first period if the degree of Knightian uncertainty is sufficiently large.

DOI： 10.1007/s11238-008-9101-7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We consider individual's portfolio selection problems. Introducing the concept of ambiguity, we show the existence of portfolio inertia under the assumptions that decision maker's beliefs are captured by an inner measure, and that her preferences are represented by the Choquet integral with respect to the inner measure. Under the concept of ambiguity, it is considered that a sigma-algebra or even an algebra is not necessarily an appropriate collection of events to which a decision maker assigns probabilities. Furthermore, we study the difference between ambiguity and uncertainty by considering investors' behavior. (c) 2006 Elsevier B.V All rights reserved.

DOI： 10.1016/j.mathsocsci.2006.07.003

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