The world population, which has reached 7.3 billion in 2015, is likely to keep on growing over the rest of the century unless a rapid and substantial reduction in the number of children borne by women in high-fertility countries is achieved soon. Those countries are home to the majority of the 225 million women who wish to delay or stop childbearing but who are not using contraception. Satisfying that unmet need for effective modern contraception would not only improve the lives of millions of women, their children, and their families, but would also reduce future population growth and thereby the human footprint on the environment.
Three types of countries according to their fertility levels
Countries can be classified into three groups according to the average number of daughters women would have who live to adulthood, given today’s fertility and mortality levels. Today, 46 percent of the world’s population lives in low-fertility countries, where fertility is below one daughter per woman. A further 35 percent of the world population lives in countries where women have, on average, between 1.0 and 1.5 daughters. Their population is still growing, but because their fertility has dropped markedly in the past and is expected to continue declining, they will likely make a relatively moderate contribution to world population growth. Lastly, 19 percent of the world population lives in countries where women have more than 1.5 daughters on average. Most of these countries are still experiencing very rapid population growth and, because their fertility has declined very slowly in the past and is even stagnating in some cases, they are expected to continue lagging behind the rest of the world in experiencing a reduction in the number of children women bear. They are therefore expected to make a very substantial contribution to future population growth and, although they currently account for a relatively small proportion of the world population, their share will likely increase substantially so that in 2100 they might account for as much as 43 percent of the world population.
Most of the 62 high-fertility countries are located in Africa, but they also appear in Asia (Afghanistan, Iraq, Jordan, Laos, the Occupied Palestinian Territory, Pakistan, the Philippines, Syria, Yemen), Oceania (the Federated States of Micronesia, Papua New Guinea, Samoa, the Solomon Islands, Timor Leste, Tonga, Vanuatu), and Latin America (Bolivia, Guatemala, Honduras, French Guiana).
The 64 intermediate-fertility countries include most of those in Latin America and the Caribbean, Northern and Southern Africa, and about half of those in Asia, including very populous countries such as India and Indonesia.
The 75 low-fertility countries include nearly all developed countries plus Tunisia in Africa; Brazil, Costa Rica, Cuba, Puerto Rico, Trinidad and Tobago, and a few other island countries in Latin America; and several countries in Asia, including populous China, Iran, Lebanon, the Republic of Korea, and most of the countries in Indochina and the Caucasus.
Thus, every world region except Europe has some countries in each of the three groups considered. It is noteworthy that there are Muslim countries with low fertility (such as Tunisia and Iran), intermediate fertility (Indonesia and Saudi Arabia), and high fertility (Jordan and Syria). Similarly, predominantly Catholic countries can be found in any of the three groups. That is, religion does not correlate strongly with fertility levels. In contrast, low levels of economic development do. Hence, poorer countries with underdeveloped social and health services and weak governance are more likely to exhibit high fertility and high levels of unmet need for contraception than the rest.
The high-fertility countries will be largely responsible for future population growth
Consideration of the three groups of countries characterized above allows us to understand their distinct roles in future population growth. According to the medium variant of the most recent set of population projections prepared by the United Nations Population Division, the world population may rise to 10.8 billion people by 2100, and most of the additional 3.5 billion people will be added to the high-fertility countries.
Because there is no certainty that any single population projection will be realized, the United Nations Population Division has produced a set of probabilistic projections that estimate the likelihood of a range of future outcomes. Information on past changes in fertility and mortality is used to model future variability in population paths. By generating thousands of future population trajectories, it is possible to determine the likelihood that the future population will fall within a certain range.
The medium-fertility variant shows that the world population will reach 10.8 billion in 2100. This variant embodies the median in the probabilistic projections, implying that there is a 50-50 chance that the population in 2100 will be higher or lower than 10.8 billion.
The probabilistic projections confirm the high potential of continued and substantial population growth in the high-fertility countries—the population of the high-fertility countries will almost certainly rise from 1.4 billion today to at least 3.6 billion in 2100, and there is a 42.5 percent chance that their population in 2100 may range between 4.7 billion and 6.1 billion. To reduce the probability of attaining that upper range, the pace of fertility decline in the high-fertility countries needs to be accelerated within the immediate future. The longer a rapid decline in fertility is delayed, the higher the eventual population size that the high-fertility countries will reach.
For the intermediate-fertility countries, there is an 80 percent probability that their 2100 population may be higher than 2.5 billion and therefore higher than it is today (2.4 billion). However, there is at least a 50-percent probability that their population may peak sometime during this century so that it may be declining long before 2100. This means that the intermediate-fertility countries are well placed to contribute to population stabilization. Nevertheless, there is still a non-trivial chance that their population will continue to grow steadily during this century. In order to avoid such an outcome, continued efforts are necessary to satisfy the unmet need for contraception in intermediate-fertility countries where the women with such need typically belong to the poorer sections of society.
Regarding the low-fertility countries, the probabilistic projections show that, given past trends, the probability that their population in 2100 will be the same or higher than it is today—3.3 billion—is just 10 percent. Yet, there is a 50-percent chance that the population reduction they experience by 2100 will be moderate. The experience of the low-fertility countries is important because they include most of the high-income countries and some of the most dynamic newly industrializing countries. Their high or rapidly rising standards of living mean that their impact on the environment is greater than that of countries in other groups. In the future, their declining populations may not only counterbalance population growth in other countries but may also moderate their environmental impact.
At the world level, continued population growth is likely
The 95 percent confidence interval indicates that the world population in 2100 will very likely be between 9.0 billion and 13.3 billion. More detailed results show that the probability that the world population may peak before 2100 is low (close to 10 percent). For the world population to remain closer to 9.0 billion in 2100, future fertility in both the high-fertility and the intermediate-fertility countries must decline faster than projected in the medium variant.
Expanding the use of contraception is key to reducing population growth
To accelerate the decline of fertility in high-fertility countries and maintain the momentum in fertility reduction in intermediate-fertility countries, it will be necessary to satisfy the current unmet need for contraception and also to create new demand for contraception where it doesn’t already exist.
In high-fertility countries, just 21 percent of women who were married or in a consensual union were using a modern method of contraception in 2010, while an additional 33 percent had an unmet need for contraception. In contrast, in low-fertility countries, 73 percent of women who were married or in a consensual union were using a modern method of contraception, and just 11 percent had an unmet need. (In intermediate-fertility countries, the respective figures were 53 percent and 21 percent.) If all countries are to reach replacement-level fertility, achieving levels of contraceptive use similar to those in low-fertility countries will be necessary. Consequently, much remains to be done to fill the gap in contraceptive use in both intermediate-fertility and high-fertility countries.
Ensuring access to modern contraception for individuals and couples in developing countries is extremely cost-effective. The benefits of being able to time desired pregnancies and avoid undesired ones are many. Women who can control their childbearing are better able to hold gainful employment and pursue educational opportunities. They are less likely to die from maternal causes or to resort to abortion. Use of contraception to lengthen the time between births improves the nutrition and survival of infants and young children. Having fewer children, families and governments can invest more in each, providing them with better nutrition, healthcare, and education.
It is estimated that family planning services in the developing world currently cost $4.1 billion. Providing modern contraceptives to all women who need them requires more than a doubling of spending, to reach $9.4 billion. The $5.3 billion difference reflects the magnitude of the improvements required to expand and improve the quality of services, particularly in low-income countries. As with current spending, a high share of the additional funds will come from the individuals who receive services and from national governments, but contributions by non-governmental organizations and donor agencies will be crucial. International support for family planning will be especially important in the low-income and lower-middle-income countries that account for 80 percent of the unmet need for contraception today. Supporting their efforts at expanding family planning is one of the most cost-effective measures available to combat poverty and improve human wellbeing.