Scientific ideas on the human population tend to be rooted in a “slow demography” paradigm, which emphasizes an inertial, predictable, self-contained view of population dynamics, mostly dependent on fertility and mortality. Yet, demography can also move fast. At the country level, it is crucial to empirically assess how fast demography moves by taking migratory movements into account, in addition to fertility and mortality. We discuss these ideas and present new estimates of the speed of population change, that is, country-level population turnover rates, as well as the share of turnover due to migration, for all countries in the world with available data between 1990 and 2020. Population turnover is inversely related to population size and development, and migratory movements tend to become important factors in shaping demography for both small and highly developed countries. Longitudinally, we analyze annual turnover data for Italy and Germany, documenting the changing speed of population change over time and its determinants. Accepting the “fast and slow” demography perspective has several implications for science and policy, which we discuss.

中文翻译：

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人口统计：快与慢

关于人口的科学观念往往植根于“慢人口”范式，该范式强调对人口动态的惯性、可预测、独立的观点，主要取决于生育率和死亡率。然而，人口结构也可以快速变化。在国家层面，除了生育率和死亡率之外，通过考虑移民流动，凭经验评估人口变化的速度至关重要。我们讨论了这些想法，并提出了对 1990 年至 2020 年间世界上所有国家的人口变化速度的新估计，即国家层面的人口流动率以及移民造成的流动比例。人口流动与人口规模和发展成反比，移民流动往往成为影响小国和高度发达国家人口结构的重要因素。在纵向上，我们分析了意大利和德国的年营业额数据，记录了人口随时间变化的速度及其决定因素。接受“快和慢”的人口统计学观点对科学和政策有几个影响，我们将对此进行讨论。