The share of the population aged 60 and over is projected to increase in nearly every country in the world during the period 2005–50. Population ageing will tend to lower both labour-force participation and savings rates, thereby raising concerns about a future slowing of economic growth. Our calculations suggest that OECD countries are likely to see modest—but not catastrophic—declines in the rate of economic growth. However, behavioural responses (including greater female labour-force participation) and policy reforms (including an increase in the legal age of retirement) can mitigate the economic consequences of an older population. In most non-OECD countries, declining fertility rates will cause labour-force-to-population ratios to rise as the shrinking share of young people will more than offset the skewing of adults towards the older ages. These factors suggest that population ageing will not significantly impede the pace of economic growth in developing countries.

The proportion of a country's population living in urban areas is highly correlated with its level of income. Urban areas offer economies of scale and richer market structures, and there is strong evidence that workers in urban areas are individually more productive, and earn more, than rural workers. However, rapid urbanization is also associated with crowding, environmental degradation, and other impediments to productivity. Overall, we find no evidence that the level of urbanization affects the rate of economic growth. Our findings weaken the rationale for either encouraging or discouraging urbanization as part of a strategy for economic growth.

We estimate the effect of fertility on female labor force participation in a panel of countries using abortion legislation as an instrument for fertility. We find that removing legal restrictions on abortion significantly reduces fertility and estimate that, on average, a birth reduces a woman’s labor supply by almost 2 years during her reproductive life. Our results imply that behavioral change, in the form of increased female labor supply, contributes significantly to economic growth during the demographic transition when fertility declines.