City populations grow due to natural change, migration, and areas that are reclassified as part of a city. Because a time series of city boundaries was not available, most analyses ignore reclassification. This paper measures reclassification in a harmonized and transparent manner by applying a new harmonized definition of cities, towns, and rural areas, called the degree of urbanization, to gridded population data between 1980 and 2020. Ignoring reclassification would attribute city population growth equally to natural change and migration. Including the effects of reclassification reveals that two‐thirds of the growth is due to natural change, followed by reclassification (29 percent), and the remainder to migration (4 percent). This demonstrates the importance of accounting for reclassification. It also underlines that discouraging migration to cities will not significantly reduce city population growth.

中文翻译：

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重新思考城市人口增长：重新分类的重要性


由于自然变化、移民和被重新划分为城市一部分的地区，城市人口不断增长。由于没有城市边界的时间序列，大多数分析都忽略了重新分类。本文通过对 1980 年至 2020 年的网格人口数据应用城市、城镇和农村地区的新统一定义（称为城市化程度），以统一和透明的方式衡量重新分类。忽略重新分类会将城市人口增长等同于自然人口增长。变化和迁移。包括重新分类的影响表明，三分之二的增长是由于自然变化，其次是重新分类（29％），其余是移民（4％）。这表明了重新分类会计的重要性。它还强调，阻止移民到城市不会显着减少城市人口增长。