What are the major drivers of population ageing? Three drivers stand out:
• Declining fertility. The world’s total fertility rate – that is, the number of children born per woman – fell from 5 children per woman in 1950 to roughly 2.5 today, and is projected to drop to about 2 by 2050. Most of this decline has occurred in the developing world, where the share of children in the population is expected to drop by half by 2050 from the 1965 level. As families have fewer children, the older-age share of the population naturally increases.
• Increased longevity. Globally, life expectancy increased by two decades since 1950 (from 48 years in 1950 to 1955 to 68 years in 2005 to 2010), and is expected to rise to 75 years by 2050. There are still considerable disparities between the wealthy industrial countries, at 82 years, and the less developed countries, at 74 years. However, this gap has narrowed greatly in the last few decades. The life expectancy of older people has increased particularly rapidly; a person who reaches age 60 has more years of life left than in the past.
• Falls in mortality came before falls in fertility. In the early phases of this transition, large cohorts were born, mainly because mortality, especially among infants and children, tended to decline before fertility fell. Those cohorts are now reaching working ages and the older ages, and their ranks will swell. In developed countries in particular, large-sized post-World War II baby-boom cohorts are reaching the older ages.
Another reason for an emphasis on ageing today is that “doomsday scenarios” abound. These alarmist views typically assume a world of static policy and institutions, continuing trends involving low fertility, and constant age-specific behaviour and labour outcomes. The resulting scenarios yield stark and shocking images of workforce shortages, asset market meltdowns, economic growth slowdowns, the financial collapse of pension and healthcare systems, and mass loneliness and insecurity.
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