Toward 7 Billion: Why World Population is Still Growing

May 2, 2005

The world’s population more than doubled in the last half-century and still is increasing. Absent an unexpected dramatic shift in family size or catastrophic increases in death rates, it could add 2.5 billion people before peaking. Worldwide, the largest group of young people ever is entering their reproductive years, requiring an expansion of family planning services to enable more couples to have the smaller families and later pregnancies they desire. In the long term, this will contribute to individual and family well-being, a slowdown in population growth and sustainable economic development.

Growth will continue...

While growth rates have fallen from their all-time high, human numbers still are increasing. The world population is growing by about 1.2 percent a year—down from a peak of roughly 2 percent in the late 1960s— but even at this lower growth rate, total population size still is steadily increasing. About 76 million people are added each year—many more than the 50 million or so added each year in the 1950s when the term “population explosion” first gained currency.

World population could reach between 7.7 billion and 10.6 billion by the mid-21st century, depending mostly on future birthrates. These United Nations (UN) projections are lower than past projections for the same period, reflecting earlier-than-expected declines in family size in some countries and increased estimates of deaths from AIDS, especially in sub-Saharan Africa. Yet even under the UN’s slow-growth scenario, population would continue to grow for at least 35 more years, to about 7.8 billion people, before declining gradually. Under the UN’s high-growth scenario, world population would exceed 35 billion late in the 23rd century and continue growing rapidly. The long-term medium projection suggests population would peak just above 9.1 billion around 2075, then drift downward to around 8.5 billion before growing again late in the 23rd century.

There is no certainty about future population trends, or even that population growth will end in the coming century. None of these population projections are reliable guides to the world’s demographic future; all are based on various, rigid assumptions. Any cessation of world population growth not driven by rising death rates would require an average global family size of close to two children per woman. Reaching such low fer­tility levels would require near-universal access to essential reproductive health services, which remain widely unavailable in many developing countries.

...and Remains Unprecedented

Population growth over the last half-century is unparalleled in the history of our planet. Human population took hundreds of thousands of years to grow to 2.5 billion in 1950. Then in just 50 years, it more than doubled to exceed 6 billion. Most of this growth has been in developing countries where advances in public health have contributed to lower mortality at all ages. Until recently, death rates fell faster than birthrates, resulting in rapid population growth.

Many poor countries struggle to maintain health care, schooling and urban infrastructure in the face of rapid population growth. Disproportionately large populations of young people that result from this growth can strain governments. They also appear to make many developing countries more vulnerable to civil conflict, especially when combined with high rates of urban population growth and shortages of cropland. Economic evidence over the past few decades makes clear that as average family size shrinks, families can save more money, and this “demographic dividend” may help well-prepared governments direct available capital to domestic economic growth.

Per capita supplies of both renewable fresh water and cropland are falling as population grows. The United Nations Food and Agriculture Organization estimates that 852 million people worldwide were undernourished in 2000-2002, and the number of chronically hungry in developing countries increased at a rate of almost 4 million people a year in the second half of the 1990s. Continuing population growth also strains water resources. By 2025, between 2.75 billion and 3.25 billion people worldwide are projected to live in countries where water scarcity or stress threaten public health and constrain food production and economic development.

Falling Birthrates, Continuing Growth

Family size is currently 2.6 children for the global “average woman”—considerably higher than the roughly 2.1-child “replacement level,” which eventually would stabilize the size of most populations.

Most industrialized countries now have an average family size of fewer than two children and are growing relatively slowly or declining in population. In eastern and some southern European countries, women have only 1.2 or 1.3 children, on average. These nations make up only a fraction of the world’s population, however, and thus have little influence on overall global trends.

Average family size in developing countries is more diverse. Poor access to family planning and the low social status of women continue to drive high rates of population growth in most of sub-Saharan Africa, in many countries of the Middle East and in parts of South Asia. Surveys show many women in these countries are having more children than they would like, or are becoming pregnant when they would prefer to wait. Growing at rates of 2.5 percent to 3.5 percent annually, these countries could double in size in 20 to 30 years.

The average number of childbirths per woman has fallen in recent decades in almost all developing countries. In some countries, the fall has been dramatic. Demographers have not explained fully this revolution in global childbearing, but improved access to family planning information and methods has played a key role. Improvements in the education of girls and the overall status of women may play among the most important roles in this demographic transition—a term that embraces decreases not only in birth rates but in death rates, as well. Parents having fewer children also may be influenced by the difficulty of providing for large families in countries where food, water, fuel and other critical natural resources are in increasingly short supply.

If the world’s average family size fell immediately to just more than two children, population still would gain several billion before stabilizing, due to the built-in momentum generated by the unprecedented number of youth entering reproductive years. In most countries, population tends to grow slowly for several decades before peaking, even when average family size hovers around replacement level and migration is not a significant demographic factor.

Population likely will continue to grow for some time, even in countries ravaged by HIV/AIDS. Especially in Africa, and increasingly in Asia and Latin America, the HIV/AIDS epidemic is contributing to higher death rates and lower life expectancies. Without significant advances in HIV prevention or in access to life-saving drugs in poor countries, deaths from AIDS are expected to increase significantly, especially in the hardest-hit African countries. UN population projections suggest that some countries will experience lower population growth rates due to the rising death toll from AIDS, but that population size in these countries still will increase significantly. One country in southern Africa—Lesotho—is a rare exception, with a population that may be peaking today and could decline at least until the middle of the century.

Is There a “Birth Dearth”? Is Population Aging a Problem?

Concerns are emerging about population aging and the possibility of population decline in countries with low fertility. Population aging— defined as a rising average age within a population—is an inevitable result of longer life expectancies and lower birthrates. In many societies, it is a positive social and environmental development, but its potential persistence to extreme average ages is worrisome to governments concerned about the funding of social security programs and general economic growth. Some studies suggest that industrialized societies tend to avoid extremely low rates of childbearing when childcare benefits are generous and men contribute significantly to housekeeping and childrearing. This is a hopeful sign for long-term population stability. Like population growth itself, population aging cannot continue indefinitely and will eventually end, even in non-growing populations.

Increases in labor participation and retirement age are more likely to smooth the transition to older societies than overt governmental attempts to boost birthrates, to the extent current population aging threatens pensions and other social security programs. Demographically strategic and modest increases in immigration rates also are options, but it is important to understand that increases in birthrates or immigration designed to maintain constant ratios of workers to retired persons can’t stop population aging for long. In order to do so, they would have to boost population growth unsustainably.

The future of fertility in individual countries is difficult to predict. Despite a long-term downward trend in fertility rates in the 1970s, countries like the United States and Sweden experienced increasing fertility rates in subsequent decades. Due to this and high rates of immigration, the U.S. population is expected to grow significantly over the next half-century; medium projections by the UN and the U.S. Census Bureau show it increasing from 296 million today to between 395 million (UN) and 420 million (Census) in 2050.

Population decline is occurring, but slowly and only in some industrialized countries. European population growth, which fueled immigration to the Americas for three centuries, has ended, and the continent’s population is in gradual decline. In East Asia, the populations of Japan, China and South Korea are likely to peak and begin a gradual decline in size before the middle of the 21st century. However, major declines outside Europe and East Asia are unlikely for decades, except possibly in one or two southern African countries especially ravaged by HIV/AIDS.

The world is demographically complex, diverse and divided in ways that have no precedent in human history. No one can say with confidence how problematic this diversity is or how humanity’s demographic future will unfold. But with an additional 76 million human beings on the planet each year, there is no foreseeable danger that the world, or any country in it, will “run out” of babies or people generally.

Impact of Smaller Families

In developing countries, children in small families tend to be better educated and healthier. Research shows that parents with fewer children invest more in each child than those with larger families.

Studies reveal that family planning reduces pregnancy-related death and illness where fertility remains high. Increased child spacing alone could reduce infant mortality by up to one-third in some developing countries.

Recent studies posit that falling family size played a critical role in the rapid economic transformation and growth of several East Asian nations, which were able to channel investment based on family-generated capital into productive and lasting industrial growth. A decline in family size also may accelerate development in other countries still experiencing high birthrates.

Low fertility rates in some developed countries have prompted claims that the absence of siblings may undermine a child’s quality of life, but even if total fertility were as low as one child per woman, there are no “siblingless” societies. Actual family size remains diverse. Many women remain childless, so many others can have two or three children without raising the average.

The quality of life for small families in developed countries is likely far better than that of large families in many poor countries, where siblings compete for food, educational opportunities and maternal care and attention.

The economic and social challenges associated with fertility decline are not comparable to those presented by rapid population growth. If low fertility rates continue, the populations of Germany, Italy, Russia and Spain could shrink by 5 percent to 10 percent by 2025—an average reduction of less than 0.5 percent per year. In contrast, the populations of countries such as the Democratic Republic of Congo, Yemen and Afghanistan, with annual growth rates near 3 percent, likely will more than double if fertility levels remain unchanged.

Need for Family Planning

The need for family planning services and contraceptives is growing more rapidly than ever. Each year, the number of people in their reproductive years grows by more than 40 million. Couples increasingly desire fewer children and need effective contraception over longer periods of their lives. These two trends translate into an increasing demand for contraceptive information, devices and services. Among married women alone, surveys suggest more than 100 million worldwide are not using contraception though they do not want to become pregnant.

The success of family planning programs over the past few decades underscores the importance of their continued support and is reflected in improved maternal and child health and rapid declines in family size and population growth. However, family planning information and services remain beyond the reach of many poor people, 1 billion of whom live on a dollar a day or less. While on average, developing countries pay 75 percent of the costs of family planning, assistance from wealthier donor countries—not just with money, but with technical expertise and contraceptives—is critical, especially in the very poorest countries.

A Better Future

Average family size is now at or below replacement level in 65 countries, including 15 developing nations. Population growth rates have fallen temporarily in the past when death rates increased because of wars, famines and epidemics. Today’s easing of population growth also includes such a component, chiefly in the rising mortality rates from HIV/AIDS in several countries, but the bulk of decline stems from lower birth rates linked to the process of modernization and to people’s aspirations for better lives.

A return to high birth rates seems improbable, although further declines could indeed be hampered by deteriorating access to reproductive health care in some regions. Over the long term, the trend toward low birth rates and low death rates is likely to yield a return to slower population growth and eventually, a population peak and a gradual, temporary decline.

This trend toward smaller families is beneficial for both developed and developing nations. In industrialized regions, where a single person consumes many times the resources consumed by an individual in the developing world, small family size helps restrain the growth of already high overall consumption levels. Meanwhile, declining birth rates in developing countries reflect dramatic improvements in the quality of life, especially for women, who increasingly go to school, enter the labor force, delay marriage and child-bearing, and have a voice in their own destiny. The evidence is overwhelming that the current trend toward smaller families and slower population growth is beneficial to the well-being of our planet and its people. It has been good for humanity, and its continuation would provide among the world’s greatest hopes for sustaining the highest possible number of human beings on earth over time.