In the past 10 years or so, there have been growing concerns in Japan that migration trends, such as large in-migration to the Tokyo metropolitan area (TMA) at the national scale and large movements from the suburbs to the centres at the metropolitan scale, have widened the core–periphery disparities at each scale under national population decline. However, the COVID-19 pandemic led to unexpected changes in these migration patterns, such as a weakened population concentration in the TMA. This study aims to examine internal migration trends from 2012, on axes of core–periphery in Japan and centre–suburbs in metropolitan areas, and the changes in the migration patterns caused by the pandemic in 2020. First, we prepared intermunicipal origin–destination tables by estimating the suppressed flows in 2012–2020 using the iterative proportional fitting technique, and then we calculated the net migration and migration efficiency indices based on seven area types: centre and suburbs of the TMA, centres and suburbs of major metropolitan areas, centres and suburbs of other metropolitan areas and nonmetropolitan areas. The results indicate that the 2020 migration efficiency in the centre of the TMA drastically dropped to the lowest level during the study period, contrasting with an upward trend in 2012–2019. The pandemic strongly affected the migration patterns from/to and within the TMA, with much net gain in the suburbs from the centre, but the impact of migration efficiencies among the other areas was minimal. These findings can help in providing direction for the postpandemic policy challenge of spatial planning in Japan, for example, the weakened but still widening disparities between the TMA and the other regions and the renewed threat of urban sprawl caused by the increased migration from the centre to the suburbs within the TMA.

中文翻译：

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2012-2020 年日本国内移民趋势：COVID-19 大流行的影响

在过去 10 年左右的时间里，日本越来越担心移民趋势，例如全国范围内大量涌入东京都市区 (TMA) 以及大都市范围内从郊区到中心的大规模迁移, 在全国人口下降的情况下，扩大了每个规模的核心-边缘差距。然而，COVID-19 大流行导致这些迁移模式发生了意想不到的变化，例如 TMA 的人口集中度减弱。本研究旨在研究自 2012 年以来日本的核心-外围轴和大都市地区的中心-郊区轴的内部迁移趋势，以及 2020 年大流行导致的迁移模式变化。首先，我们通过使用迭代比例拟合技术估计 2012-2020 年的抑制流量来准备城市间的起源-目的地表，然后我们根据七种区域类型计算净迁移和迁移效率指数：TMA 的中心和郊区、中心和郊区主要大都市区、其他大都市区和非大都市区的中心和郊区。结果表明，2020 年 TMA 中心的迁移效率急剧下降至研究期间的最低水平，与 2012-2019 年的上升趋势形成鲜明对比。大流行病强烈影响了 TMA 的迁出/迁出和迁入模式，郊区从市中心获得了很多净收益，但其他地区迁徙效率的影响微乎其微。