要旨：Land is everywhere, being the substratum of our existence. In addition, land is intimately linked to the dual concept of location in human activity. Together, land and location are essential ingredients for the lives of individuals as well as for national economies. Today, there exist two different approaches to incorporating land and location into a general equilibrium theory. Dating from the classic work of von Thünen (1826), a rich variety of land-location density models have been developed. In a density model, a continuum of agents is distributed over a continuous location space. Given that simple calculus can be used in the analysis, these density models continue even today to be the “workhorse” of urban economics and location theory. However, the behavioral meaning of each agent occupying an infinitesimal “density of land” has long been in question. Given this situation, a radically new approach, called the σ-field approach, was developed in the mid 1980s for modeling land in a general equilibrium framework. In this approach: (i) the totality of land, L, is specified as a subset of R^2, (ii) all possible land parcels in L are given by the σ-field of Lebesgue measurable subsets of L, and (iii) each of a finite number of agents is postulated to choose one such parcel . Starting with Berliant (1985), increasingly more sophisticated σ-field models of land have been developed. Given these two different approaches to modeling land within general equilibrium framework, several attempts have thus far been proposed for bridging the gap between them. But while a systematic study of the relationship between density models and σ-field models remains to be completed, the clarification of this relationship could open a new horizon toward a general equilibrium theory of land.

要旨：This study analyzes how local agglomeration affects the probabilities of firm entry and exit by focusing on single-establishment firms in the service sector. Firms in the service sector face geographically localized markets since service is generally non-tradable. A theoretical prediction in the literature is that firm turnover is increasing in market size, which is empirically tested in this paper. A novelty of this study is to identify geographic ranges of local agglomeration with geocoding of firm location and micro-geographic data. This study finds that probability of firm entry and exit in the service sector is largely affected by agglomeration factors localized within a 3km radius from their locations.

要旨：In international trade, transportation requires a round trip for which a transport firm has to commit to shipping capacity that is sufficient to meet the maximum shipping volume. This may cause the “backhaul problem.” Trade theory suggests that, facing the problem, transport firms with market power adjust their freight rates strategically when import tariffs change. As a consequence, a country reducing its import tariffs may experience an increase in exports as well as imports. Using worldwide data covering 1995-2007, we find evidence that supports these predictions: a 1% reduction in an importer’s tariffs increases the import freight rates by around 0.8%; reduces the export freight rates by around 1.1%; and increases the export quantity by 0.6% to 1%. These findings indicate a new mechanism through which import-tariff reductions lead to export expansions.

要旨：地域格差は学術的にも政策的にも旧くて新しいテーマである。戦後日本において国土の均衡発展は一貫した政策目標であったが，2000年代になると世界的な都市間競争を念頭に，規制緩和による都市再生政策が推進されるようになった。一方，現在政府が取り組む地方創生政策は地方圏の経済的疲弊と東京一極集中の是正を通じ人口減少の克服を目指すものであるが，今後その成果の検証が求められよう。地域格差の拡大をめぐって議論がしばしば混乱する理由に，格差現象を把握する概念の不明確さがある。すなわち，人口や所得が地理的に偏って存在することを問題とする「規模の地域間格差」と，人口や世帯あたりで見た所得の差を問題とする「水準の地域間格差」の区別が重要である（豊田,2013）。新古典派経済学の理論によると，労働力の移動が自由であれば，低賃金地域（地方圏）から高賃金地域（大都市圏）へ人口が移動する。その結果，市場の調整メカニズムにより賃金は均衡に向かい「水準の地域間格差」は縮小する。しかし，前者からは人口流出が，後者へは人口流入が生じ，「規模の地域間格差」は拡大する。もし人口移動を制限する政策をとるならば，前者で失業増大，後者では人手不足が生じ，全体の成長が阻害されよう。二つの格差がつねにトレードオフ関係にあるとは限らないが，現実の状況には同時に解決しがたいジレンマが存在する（豊田,2015）。所得の地域格差に関するこれまでの研究では，1993～2008年の都道府県別世帯所得の分析から，所得水準の地域間格差は縮小したが，人口移動が規模の地域間格差を拡大していることを指摘した（豊田,2013）。その後，2008年のリーマンショックや2011年の東日本大震災に伴う深刻な景気の後退を経て，日本経済は緩やかな景気回復過程が続いている。この間，日本社会は人口減少局面への突入，戦後団塊世代の引退，非正規労働者の増加など大きな変化を経験した。本研究では，直近の雇用や所得の地域格差は拡大しているか，それが人口移動にどのような影響を与えているか分析をおこなう。

【国際経済学セミナーと共催】
要旨：International trade and investment flows obey gravity relationships, posing a continuing puzzle. New data on cross-border commercial real-estate investment flows show that they obey gravity, but this relationship is rendered insignificant by controlling for the presence of counterparties from origin countries in destination countries. We attribute this to a strong, robust tendency for preferential matching with same-country counterparties. We set up an equilibrium matching model with a contracting/trust friction affecting different-nationality transactions. The model explains the persistent success of gravity using the friction and the fact that the spatial distribution of same-nationality counterparties is well-explained by historical links between countries.