要旨：Pandemic of COVID-19 required to change our lifestyles to contain or mitigate the spread of infectious diseases. Various Non-pharmaceutical intervention (NPI) measures have been implemented in the situation that no effective treatment or vaccine has been established. New methods for monitoring the spread of infection have been proposed based on the recent technological and theoretical developments. In this talk, I review basics of mathematical models of infectious diseases and recent topics related with NPIs, and report and discuss some results on the effects of NPIs and the future perspective.

要旨：本研究は定量的空間経済モデル（quantitative spatial economics models）のパラメータを完全情報最尤推定（full information maximum likelihood, FIML）によって推定する新しい手法を提案する。内生変数の観測値から外生的な構造的残差（structural residuals）を一意に求められるモデルに対して、提案手法は適用可能である。構造的残差が確率分布に従うという仮定の下で、対数尤度関数を構築できる。提案手法は操作変数を必要としない。提案手法は、クロスセクションデータとパネルデータの双方に適用可能である。提案手法は、多くの場合において、パラメータの推定値を空間均衡が安定になる範囲に制約すると考えられる。本研究は、提案手法を二種類のデータに対して適用することにより、その有効性を確認する。一つ目は、既知のパラメータを有するモデルから発生させた実験データであり、二つ目は、1975年から2015年にかけての日本国内の観測データである。

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.