The present paper examines the welfare effect of ex post rate-of-return regulation. Unlike the traditional rate-of-return regulation on a monopoly, the regulation is mainly for oligopolistic industries and of the ex post nature. At the end of each year, total revenue of the firms as a whole is calculated. If the revenue is greater than the revenue requirement of all firms, a portion of the excess is taxed from the firms according to a certain prescribed rule. On the other hand, if the revenue falls short of the revenue requirement, the agency subsidizes the firms for the shortage. It is shown how the regulation affects social welfare by creating an artificial competitive environment for the firms and by controlling industry cost efficiency. The optimal regulation is also analyzed.

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In this paper I examine the welfare effects of tariffs in international free-entry oligopolies under integrated markets in a two-country world model. I shall show that a small specific (or ad-variorum) tariff imposed by the home country exercises the same welfare effect as a small specific (or ad-variorum) tariff imposed by the foreign country in a free trade equilibrium. These unilateral specific (or ad-variorum) tariffs and reciprocal specific (or advariorum) tariffs make the home and the foreign countries better off if demand functions of oligopolistic goods are concave (or concave or linear). (JEL No. 411, 611)

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The purpose of this paper is to analyze the appropriate stabilization rules among a large number of countries. By decomposing the world system into one aggregate and N-1 difference systems, the paper calculates the desirable monetary rules in the N-country model. we find that the optimal monetary rule is a combination of the global monetary rule and the intervention rule. In general, the derived rule depends on the number of countries and the relative magnitudes of exogenous variances. The paper first analyzes the symmetric world economy and extends the results to the asymmetric world.

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This paper considers the issues of gradual reform of not only commodity tax but also factor tax. Using the two-sector model, a simple rule of tax reform is proposed, after the effects of changes of tax rates on the social welfare are examined. This rule, which is expressed in terms of observable economic variables, is applicable however tax rates may be assigned.

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This paper examines the economic role of mandatory disclosure in a noisy rational expectations model. Many theoretical studies of discretionary disclosure suggest that firms never have the incentive to spend less on disclosure than is socially optimal and offer no support for mandatory disclosure regulations.
This paper, however, derives the paradoxical result that mandatory disclosure may increase the social surplus even when firms have the incentive to spend more on disclosure than is socially optimal. The reason is that mandatory disclosure may increase the cost of disclosing too much information and discourage firms from making this overdisclosure decision.

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The purpose of this paper is to make a empirical analysis of the adjustment speed of the bank loan rate. The crucial changes occurred in recent Japanese loan market. The previous studies showed that the adjustment speed of the bank loan rate increased. They estimated the parameters of a linear regression system obeying different regimes. They have a problem in that the regressions arn likely to be contaminated with observations from the other regimes. This paper circumvents this problem by a finding the switching points in time using the simulation method.

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