A large literature documents how cities vary in their skill structure and how this has implications for their economic growth. By contrast, how cities vary in their age structure and the potential implications of this for their economic growth has been a hitherto largely neglected research area. Using novel data from a variety of historical and contemporary sources, we first show that there is marked variation in the age structure of the world's largest cities, both across cities and over time. We then study how age structure affects economic growth for a global cross-section of mega-cities and find that mega-cities with higher dependency ratios - i.e. with more children and/or seniors per working-age adult - grow slower. Overall, and despite the many data and econometric challenges posed by this type of analysis, we advocate for more research on the subject given its importance.

大量文献记录了城市的技能结构如何变化以及这如何影响其经济增长。相比之下，城市的年龄结构如何变化及其对经济增长的潜在影响一直是迄今为止被广泛忽视的研究领域。我们使用来自各种历史和当代资源的新颖数据，首先表明，全球最大城市的年龄结构在不同城市之间以及随着时间的推移都存在明显的差异。然后，我们研究了年龄结构如何影响全球各大城市的经济增长，并发现，抚养比较高的大城市（即每个工作年龄的成年人有更多的儿童和/或老年人）的增长速度较慢。总体而言，尽管此类分析带来了许多数据和计量方面的挑战，