要旨：Most metropolitan areas in the U.S. have been developed around the automobile, making driving essential to accessing opportunities.  Despite high rates of driving, some adults do not drive.  A majority of non-drivers face significant barriers to driving, one of which is state driver’s license regulations that deny driving privileges to unauthorized immigrants. However, 15 states and the District of Columbia have adopted laws allowing unauthorized immigrants to acquire driver licenses and, therefore, to legally drive.  In this study, we draw on annual data from the American Community Survey from 2006 to 2018 to examine the relationship between the adoption of state driver’s licensing laws for unauthorized immigrants and changes in automobile commuting and commuting by public transit.  We focus on unauthorized Latinx immigrants in California, the state with the largest percentage of unauthorized residents.  We then test to see whether the effects are similar in other states that have recently adopted comparable driver’s licensing regulations. Many unauthorized immigrants in California have obtained driver’s licenses through Assembly Bill 60 (AB 60) allowing them to drive legally. Our analysis shows that AB 60 had a small positive effect on auto commuting and a small negative effect on transit commuting among unauthorized Latinx immigrants in California but, likely, little or no effect in states outside of California. Combined with its role in reducing hit and run accidents and potentially easing immigrants’ fears of police stops, the evidence suggests that AB 60 has contributed to the enhanced mobility and safety of unauthorized immigrants and their families.

要旨：神戸市全体の大規模交通シミュレーションを実行した結果、交通量に対して道の本数をプロットすると、冪的な関係に従うことが明らかとなった。その起源について数学的なモデルを立て、冪的な分布が生じた理由について考察する。また、阪神高速のETCデータを分析したところ、ODには強固な規則性が存在することが示唆されたが、2020年にはCOVID19の影響により規則性が破れている様子が観察されたため、これについても報告する。

《参考資料》

Umemoto and Ito, Journal of Computational Social Science, 2018

Umemoto and Ito, Journal of Computational Social Science, 2019

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要旨：We construct a model in which there are oligopolistic firms that can influence the aggregate market conditions and monopolistic firms which cannot influence the aggregate market. We assume that both types of firms can conduct R&D investments to improve their productivities. When the R&D cost of oligopolistic firms is sufficiently lower than monopolistic firms, oligopolistic firms can survive as big firms, which can manipulate the market, dominate the market and conduct the larger R&D investments. We show that with the increase in the market size, the relative outputs and R&D investments of oligopolistic firms compared to monopolistic firms are raised, and consequently, the survival of big firms becomes easy. We show that there is a subsidy policy that enables the economy to achieve the second-best allocation.