Baby boom and baby bust seen in latest world fertility rates

Published 29 November 2018

Global fertility rates have declined substantially since 1950. Currently in many nations, fertility rates are not high enough to maintain current population levels, but in others, largely in sub-Saharan Africa, high fertility rates are still driving population increases.

Total fertility rates, which represent the average number of children a woman delivers over her lifetime, have substantially declined in most countries since 1950. In 2017, 91 countries (including Singapore, Spain, Portugal, Norway, South Korea, and Cyprus) had rates lower than two and were not maintaining their current population size, while 104 nations were seeing population increases as a result of their continuing high fertility rates. The lowest rate was in Cyprus, where, on average, a woman would give birth to one child throughout her lifetime, as opposed to the highest, in Niger, with a total fertility rate of seven children.

The results come in the latest estimates from the Global Burden of Disease study, published in The Lancet in November and funded by the Bill and Melinda Gates Foundation, concluded from the evidence of seven separate studies that global progress in health - including fertility - is not inevitable.(1)

'These statistics represent both a "baby boom" for some nations and a "baby bust" for others,' said Dr Christopher Murray, Director of the Institute for Health Metrics and Evaluation at the University of Washington, USA, where the studies were coordinated. 'The lower rates of women's fertility clearly reflect not only access to and availability of reproductive health services, but also many women choosing to delay or forgo giving birth, as well as having more opportunities for education and employment.'

Among its many findings, this complex study found that, despite an overall fall of 49.4% in total fertility rate (from 4.7 live births to 2.4), global population has been increasing by an average of 83.8 million people per year since 1985, and in 2017 was put at 7.6 billion (up from an estimate of 2.6 billion in 1950). However, at the national level total fertility rate did decline in all countries between 1950 and 2017; in 2017 rates ranged from a low of 1.0 live births in Cyprus to a high of 7.1 live births in Niger.

However, the authors note that 'total fertility rate' masks variation in trends in fertility at different ages and in different countries. Thus, age-specific fertility rate in women up to the age of 25 was lower than that in women of an older age. Similarly, of the 59 countries with a total fertility rate of more than three live births per woman in 2017, 41 were in sub-Saharan Africa. Of the remainder, six countries were in north Africa and the Middle East.

By contrast, the study found that 33 countries have been in overall population decline since 2010, including Estonia, Ukraine, Belarus, Greece, Georgia, Bulgaria, Romania, and Spain. Many other countries, say the authors, are also likely to have decreasing populations as the size of their birth cohorts reduces. Population decline and the associated shift to an older population has profound cultural, economic, and social implications, they note.

And, while the study offers no detailed explanation for the decline in fertility rate, the authors do note that options to deal with the social and economic consequences of population decline include pro-natalist policies (which in a few countries have included state-funded IVF), liberal immigration policies, and increasing the retirement age.

1. GBD 2017 Population and Fertility Collaborators. Population and fertility by age and sex for 195 countries and territories, 1950–2017: a systematic analysis for the Global Burden of Disease Study 2017. Lancet 2018; 392: 1995–2051.