要旨：This paper proposes a framework where commercial activities emerge endogenously through merchants' market-oriented investments. Merchants buy goods from producers by offering the bid-price, and hold them as an inventory for sale to consumers by setting the ask-price. Competition amongst merchants generates a tradeoff, when they expand business, in which excess inventories entail a loss from their remaining unsold while a deficit of stock loses a sale foregone. The steady-state equilibria are shown to display an interesting multiplicity in which the optimal level of merchants' inventory holdings interacts with the bid-ask spread or the markups. In more commercialized equilibria, merchants are large-scaled, attract a large number of consumers, and restock inventories by a low price, while in less commercialized equilibria, merchants are small-scaled, attract only few consumers, and restock inventories by a high price. We show that producers, who are less skillful in selling goods, attract inefficiently large number of buyers in the latter equilibria than in the former, and thereby that the division of labor between production and commerce enhances the allocation efficiency and overall welfare. We find that such a division of labor can be limited by the extent of the total size of market. Further, producers' decision to become merchants will also be discussed.

要旨：We study an equilibrium for a product-differentiated market in which oligopolistic firms and monopolistically competitive firms coexist. We assume that the number of monopolistically competitive firms changes given the number of oligopolistic firms and the equilibrium size is determined when no firms earn positive profits. We show that there may exist multiple equilibria, and the size of monopolistically competitive firms decreases and social welfare level increases as the number of oligopolistic firms increases.

要旨：Though road pricing equal to social marginal cost is the best instrument to reduce the congestion, it is considered as impractical one by political reason. Thus instrument to shift the auto uses to other modes is one of alternatives. In this paper, we investigated optimal bus services regarding fare and frequency under constraint of real world, where auto is under-priced. And bus services under the zero profit constraint and under the provision by monopolistic operator were also investigated. We showed that even though optimal bus fare depends on the type of bus provision, the optimal rule to determine the bus frequency is same. Furthermore recent experience in London gives rise to the policy questions about the bus service policy. Thus by comparative analysis, we investigated that how the optimal bus service should change against the increase in road toll. We showed that bus fare should increase when toll level gets increased except the case of zero profit constraint. And we also showed that optimal bus frequency and load factor increase regardless of types of provision.

要旨：Despite the airport privatization and deregulation trend in recent years, whether or not the privatized or commercialized airports should be left unregulated is still an open question. Related to this issue, one question that has received a very little attention to date is if and how pricing behavior of unregulated airports affect downstream airline competition, especially the competition between airlines offering differentiated services such as the case of full service airlines (FSA) vis-à-vis low cost carriers (LCC). If the upstream monopoly (airport) hinders downstream (airline) competition, the welfare effects of the upstream unregulated monopoly may be much larger than initially suspected. This aspect of airport pricing has not been formally incorporated in the debate on airport price regulation. In this paper, we study a duopoly model to capture the differential competitive effects of changing airport user charges on FSAs and LCCs. By making reasonable assumptions on differential price elasticities, unit costs and competitive behavior as manifested by firm-specific conduct parameters, we perform numerical simulations to measure differential effects on an FSA and an LCC of increasing airside user charge by an unregulated upstream monopolist airport. Our analytical and numerical results suggest existence of the asymmetric effects of an airport’s monopoly pricing on LCC and FSA. That is, LCCs suffer more from an identical cost increase than FSAs and are, therefore, more vulnerable to monopolistic pricing practices of an unregulated airport. This implies that unregulated airport pricing would reduce the extent of competition in downstream airline markets, and thus, cause a further detrimental effect on welfare over and above the first-order dead weight loss of airport’s monopolistic pricing. Considering that LCCs have brought considerable reduction of average fares and the associated welfare gains, it is important for the governments to take into account of these asymmetric effects of increasing airport user charges on FSAs and LCCs when they consider the form and extent of regulation or deregulation. Although our model and simulation work deal specifically with the effect of airport pricing on downstream airline markets, our framework of analysis may be applicable to analysis of any policy affecting costs of FSAs and LCCs including security levies as well as potentially adaptable to other upstream-downstream industry cases.

要旨：本報告が依拠するモデルでは、非熟練労働者が技能労働者になるには固定費用が発生するため、規模の経済が存在する。しかし多くの技能労働者があつまる場所では、固定費用が軽減され、追加的な技能労働者形成がより容易になる。技能労働者を雇用する近代産業は技能労働者のバラエティの拡大によって生産コストが低下する外部効果を得る。一方、技能労働者が多くなれば、彼らの間の競争が増すので収入は逓減し、非熟練労働者が相対的に不足してくるので実質賃金格差は縮まる。これを２地域空間に適用すると、技能労働者が雇用される近代産業がどちらか一方に集中する核－周辺構造が成立することが確認される。周辺地域で近代産業を設立しようとしても、各地域の集積の経済が強く、低賃金だけでは十分な競争力を有さないからである。技能労働者が育っていない周辺地域で技能労働力を養成する固定費用の高さも障害になる。ただし、地域を越えて技能のスピルオーバーがある場合に、これを利用して技能労働力を涵養して、そのような障壁を乗り越える可能性は高まる。

要旨：出発時刻選択問題における動的な均衡状態の導出方法、均衡状態と最適状態の関連、均衡状態の存在についての定理とそれらの関連を示す。出発時刻選択問題は道路における渋滞を費用最小化原理と均衡状態を前提として理論的に解析するための枠組みであり、これまでいくつかの研究により解法が示されている。しかしこれらの研究では費用関数に強い制約が課せられていた。この研究では、利用者の選択する経路上に存在するボトルネックが１つだけしかない場合において、費用関数の前提条件を緩和した上で出発時刻選択問題の解法および均衡状態のもつ数理的な性質を示す定理を導出する。

要旨：This paper presents an analytical framework for understanding an efficient usage of ODA to attract foreign investment, based on an economic geography model. One of the main results is that recipient countries with less trade openness should have their ODA directed more towards social infrastructure, whereas it should be shifted towards economic infrastructure if undergoing trade liberalization. The second result is that the foreign investment may outflow temporarily from less developed countries in the process of globalization. Finally, we demonstrate that these findings are consistent with statistical evidence using a dataset of 78 recipient countries for the period during 1991-2001.

要旨：日本における空港・港湾の整備と運営に関わる問題を、規模の経済、輸送頻度の経済、および補完性という概念に基づき整理した。その上で、日本においては、輸送機能を特定の空港・港湾により集中させることが望ましいと考えられることを指摘した。そのために必要なキャパシティの確保の方法について検討し、その利点と欠点について検討した。

要旨：We propose a class of Chamberlinian monopolisitic competition models that yields: (i) simple closed-form solutions for the price equilibrium; (ii) equilibrium prices which increase with production costs, increase with consumption expenditure, and decrease with the mass of competitors. We illustrate this approach with a 'constant absolute risk aversion' specification and then apply it to international trade and economic growth.

要旨：本論文では、生産において環境汚染を排出するような工業財部門とニューメレールとしての農業財を生産する2 部門の小国経済モデルを考察する。 さらに、工業財はその規模に応じて収穫一定の伝統的技術と収穫逓増の先進技術が選択可能なケースを設定する。このもとで経済全体を考える政府が汚染を排出する工業財部門に適切な環境政策をとった場合、排出される汚染は多くの実証分析で証明されてきた環境クズネッツ曲線が導出でき、その要因が工業財部門の技術の選択と関係があることを示す。 また、地域間の人口移動が生じるようなケースのついても考察し長期の地域分布にどのような影響が生じるかについて検討する。