世界发展银行-Cities-of-Workers,-Children,-or-Seniors_-Age-Structure-and-Economic-Growth-in-a-Global-Cross-Section-of-Cities_56页_3mb

Summary of "Cities of Workers, Children, or Seniors? Age Structure and Economic Growth in a Global Cross-Section of Cities"

Core Content

This paper investigates the relationship between a city's age structure and its economic growth, highlighting that while the role of a city's skill structure in economic growth is well-documented, the impact of age structure has been largely overlooked. The study focuses on the global cross-section of mega-cities and proposes that cities with a higher share of children or seniors tend to experience slower economic growth compared to those with a higher share of working-age adults.

Main Points

• Age Structure and Economic Growth: Cities with a higher child or aged dependency ratio grow more slowly. This is due to both direct and indirect effects.
• Direct Effects: A higher dependency ratio reduces the share of working-age adults, which in turn lowers GDP per capita since working-age adults are more productive and work more hours.
• Indirect Effects:
  • Intra-household effects: Children and seniors may reduce the time working-age adults spend working and increase their opportunity cost of leisure. This can lower productivity and GDP per capita.
  • City-wide effects:
    • Human capital externalities: Higher dependency ratios reduce the frequency of interactions among working-age individuals, weakening knowledge spillovers and productivity.
    • Crowding effects: More children and seniors can lead to increased congestion and strain on public services, which may negatively impact education and health outcomes.
    • Public expenditure effects: Cities with higher dependency ratios may allocate more resources to non-productive public goods, such as schools and playgrounds, and less to infrastructure that supports economic growth.

Key Findings

• Cities with a higher proportion of children (child dependency ratio) show a more significant negative impact on economic growth than those with a higher proportion of seniors.
• The effects of child dependency ratios on growth are more pronounced in the short run, but they tend to disappear as children grow older and enter the workforce.
• The paper uses a novel dataset of 655 mega-cities, covering the period from 1787 to 2016, and applies various identification strategies to isolate the effect of age structure on economic growth.
• The analysis is based on night lights data (1996-2011) to measure economic growth, with age structure data collected from multiple sources including census records, OECD databases, DHS surveys, and I2D2.

Methodology and Data

• Data Collection:
  • The authors compiled data on age structure from historical and contemporary sources, including IPUMS, census reports, OECD, DHS, and I2D2.
  • They focused on "urban agglomerations" as defined by the United Nations, which includes central areas, suburbs, and satellite towns.
• Sample Sizes:
  • Descriptive Analysis Sample: 4,907 city-year observations across 139 countries.
  • Econometric Analysis Sample: 351 mega-cities with age structure data circa 1990.
• Age Structure Measures:
  • Child dependency ratio: children (0–14) to working-age adults (15–64).
  • Aged dependency ratio: seniors (65+) to working-age adults.
  • Total dependency ratio: sum of child and aged dependency ratios.

Contributions to Literature

• Local Determinants of Economic Growth: The paper adds to the literature on agglomeration effects and human capital spillovers by emphasizing the role of age structure in shaping productivity and growth.
• Urbanization without Growth: It contributes to the understanding of urbanization in developing countries, where cities may grow rapidly in population but not in economic terms.
• Macro Demographic Effects: The study expands on the macroeconomic literature on age structure and growth by examining the city-level implications of demographic changes.

Limitations and Caution

• The paper acknowledges that while it isolates age structure effects, it cannot fully rule out endogeneity. Thus, the findings are suggestive rather than definitive.
• It does not make policy recommendations but aims to raise awareness about the potential role of age structure in city growth.

Conclusion

The paper presents a comprehensive analysis of how age structure affects economic growth in cities, offering insights into the mechanisms that link demographic composition to productivity and development. It underscores the need to consider age structure as a key determinant of urban economic performance and highlights the importance of understanding cities as complex entities with diverse demographic profiles.