"A Simple Axiomatization of Iterated Choquet Objectives"

A set of axioms which characterizes a preference representable by the iterated Choquet expected utility is presented. This objective function is attractive since it possesses a feature of dynamical consistency. Furthermore,we show that under the same axioms the conditional preference is represented by the Choquet expected utility with respect to the capacity which is updated according to the Dempster-Shafer rule. We do this by weakening Schmeidler's axiom of comonotonic independence to our axiom of constrained comonotonic independence and by adding the axiom of dynamical consistency.

"Search under the Knightian Uncertainty"

Suppose that "uncertainty" about labor market conditions has increased. Does this change induce an unemployed worker to search longer, or shorter? This paper shows that the answer is drastically different depending on whether an increase in "uncertainty" is an increase in risk or that in true uncertainty in the sense of Frank Knight. We show in a general framework that, while an increase in risk (the mean-preserving spread of the wage distribution that the worker thinks she faces) increases the reservation wage, an increase in the Knightian uncertainty (a decrease in her confidence about the wage distribution) reduces it.

"Economics of Self-Feeding Fear"

A model of self-feeding fear is presented. Suppose that an economic agent is (1-ƒÃ)~100% certain that uncertainty she faces is characterized by a particular probability measure, but that she has a fear that, with ƒÃ~100% chance, her conviction is completely wrong and she is left perfectly ignorant about the true measure in the present as well as in the future. We call this situation ƒÃ-contamination of confidence. In this situation, if the economic agent follows Bayesian procedure or its variant, which is considered as rational in the theory of economics, her confidence erodes after having new observation.

"Distortion in Land Price Information---Mechanism in Sales Comparables and Appraisal Value Relation---"

This paper investigates the nature and magnitude of distortion in land price information publicly available in Japan, especially in the Published Land Price of the Japanese Government. After examining characteristics of various land price information in Japan, we construct hedonic price indexes based on both actual transaction prices and Published Land Prices, and compare them to find possible distortion in the governmental price information. We find a large and systematic discrepancy between actual transaction prices and Published Land Prices, suggesting serious problems in the governmental information system. We also consider possibility of structural change in the Japanese real estate markets, and examine its effect on price indexes.

"Does e-Commerce Always Increase Social Welfare in the Long Run?"

We examine the effect of electronic commerce ("e-commerce") on social welfare, in the framework of conventional spatial competition models. We consider the case where both conventional and electronic retailers coexist in equilibrium. We show that e-commerce does not necessarily increase social welfare in the long run. In particular, when electronic retailers have clear cost advantage over conventional retailers, then the advent of e-commerce is shown to reduce social welfare.

"An Axiomatic Approach to ƒÃ-contamination"

Suppose that an economic agent is (1|ƒÃ)~100% certain that uncertainty she faces is characterized by a particular probability measure, but that she has a fear that, with ƒÃ~100% chance, her conviction is completely wrong and she is left perfectly ignorant about the true measure in the present as well as in the future.This situation is often called "ƒÃ-contamination of con dence." The purpose of this paper is to provide a simple set of behavioral axioms under which the decision-maker's preference is represented by the Choquet expected utility with the ƒÃ-contamination of con dence.

"Liquidity Motives of Holding Money under Investment Risk: A Dynamic Analysis"

Jones and Ostroy (1984) argue that money,as an asset of the least transaction cost, offers exibility to its holder, which other assets cannot provide. We extend the idea of Jones and Ostroy into a truely dynamic framework of infinite horizon with a risk-neutral decision-maker. We then investigate the effect of an increase in investment risk on the demand for liquidity a la Jones and Ostroy. In particular, we prove that the opitmal strategy exists, that it has a reservation property, and that the reservation value increases when investment risk increases in the sense of a mean-preserving spread. While the effect of a mean-preserving spread on the reservation value is unambiguous, its e ect on money demand is ambiguous. We then provide conditions on increasing investment risk under which money demand unambiguously increases.

"Irreversible Investment and Knightian Uncertainty"

When firms decide about irreversible investment, they may not have perfect confidence about their perceived probability measure describing future uncertainty. They may think other probability measures perturbed from the original one are also probable. Uncertainty characterized by not a single probability measure but a set of probability measures is called Knightian uncertainty. The effect of Knightian uncertainty on the value of irreversible investment opportunity is shown to be drastically different from that of the traditional uncertainty in the form of risk. Specifically, an increase in Knightian uncertainty decreases the value of investment opportunity while an increase in risk increases it.

"A Note on Learning under the Knightian Uncertainty"

In contrast to the traditional model of uncertainty, where the uncertainty is characterized by a single distribution function that a decision maker faces, the Knightian-uncertainty approach characterizes it as a set of distributions rather than a single one. Hence, learning in the context of Knightian uncertainty is characterized by an update process of the set of distributions after each of random sampling. This note presents two examples in which the Dempster-Shafer update rule, the one which attracts much attention since it seems intuitive, does not at all reduce the Knightian uncertainty (Example 1) and it actually increases the Knightian uncertainty (Example 2). Thus, what is a sensible update process is still an open question under the Knightian uncertainty.

"Innovation Versus Diffusion: Determinants of Productivity Growth Among Japanese Firms"

This paper presents a model of firm-level productivity growth that distinguishes between innovation and technology diffusion, and then applies the model to a large-scale data set of Japanese manufacturing and non-manufacturing firms between 1994 and 2000. We find both innovation and diffusion are important factors in firm-level productivity growth. Results also suggest that innovation comes not only directly from R&D activities, but also indirectly from patent purchases and imports. Previously, patent purchases and imports were considered as sources of technology diffusion rather than innovation. In fact, we find patent purchases are more effective in this regard than R&D expenditure.