要旨：We criticize the theories used to explain the size distribution of cities. They take an empirical fact and work backward to obtain assumptions on primitives. The induced theoretical assumptions on consumer behavior, particularly about their inability to insure against the city-level productivity shocks in the model, are untenable. With either self insurance or insurance markets, and either an arbitrarily small cost of moving or the assumption that consumers do not perfectly observe the shocks to firms' technologies, the agents will never move. Even without these frictions, our analysis yields another equilibrium with insurance where consumers never move. Thus, insurance is a substitute for movement. We propose an alternative class of models, involving extreme risk against which consumers will not insure. Instead, they will move, generating a Frechet distribution of city sizes that is empirically competitive with other models.

【応用ミクロ経済学・産業経済学ワークショップと共催】

要旨：There is increasing empirical evidence that vertical product differentiation is an important determinant of international trade. However, the economic literature so far has solely focused on the case in which quality trade stems from differences between countries. No studies investigate the role of quality trade between similar economies. This paper first develops a simple theoretical trade model that includes vertical product differentiation in a heterogeneous-firm framework. The model yields three main predictions for trade between similar economies. First, exported goods are of higher quality than goods sold on the domestic market. Second, larger economies have on average higher export qualities compared with smaller economies. Third, with increasing trade costs higher quality goods are exchanged. For all three effects, strong empirical support is found using detailed export trade data of the United States and 15 European Union countries.

要旨：This paper aims to address the effects of congestion externalities in a new economic geography context. Our model is the same as the standard CP model except for the assumption that per-unit interregional transport cost depends on total volume of shipped varieties. As a result of the endogeneity of per-unit transport cost, we have some features of agglomeration and dispersion equilibria that are not evident from the standard models. A welfare analysis focuses on a second best problem so that a market still can take a part in generating agglomeration economies. That is, we investigate the relationship between the congestion externalities and the second best unit tax of shipped goods given firm's monopolistic pricing. If skilled workers are nearly agglomerated in one region, the interregional congestion externalities should not be fully internalized regardless of the level of transport technology. In an evenly dispersed economy, however, the second best tax can be larger than the congestion externalities if the level of transport technology is low.