Populations around the world are aging, as mortality and fertility rates fall.

While increased longevity represents a remarkable achievement of modern medicine and public health, the steep decline in fertility over the past decades is cause for concern.

The collapse in birth rates can be attributed to powerful structural factors — such as urbanization, education gains and women’s increased participation in the labor market — as well as the perception that childbearing is more manageable with a smaller number of children. As a result, governments’ efforts to reverse the trend have fallen short.