(July 2010) World population has reached a transition point: The rapid growth of the second half of the 20th century has slowed. But factors such as continuously improving mortality and slower-than-expected declines in birth rates guarantee continued growth for decades.

The questions remain: how fast, how much, and where? The declines in birth rates and increased longevity has led to a concern in more developed countries and one that will soon spread to less developed countries: The proportion of the elderly population has been rising and will continue. The pressure on national pension plans and long-term health care has increased as the support ratio, the number of those ages 15 to 64 compared with those ages 65 and over, decreases.The population size of the world's more developed countries has essentially peaked.

What little growth remains will mostly come from immigration from less developed countries. A number of more developed countries are likely to decline in size and see the proportion of their elderly populations rise to unprecedented levels. The outlook for less developed countries is quite different. The increase in world population from 1.6 billion in 1900 to 6.1 billion in 2000 was almost entirely due to population growth in those countries. The 20th-century population "explosion" was a direct result of the rapid decline in mortality rates in less developed countries. Achievements in rising life expectancy that had taken centuries in Europe took mere decades in many less developed countries. As less developed countries' growth rates rose to levels never experienced in the more developed countries, many adopted policies to lower the birth rate to keep pace with rapidly declining death rates. In the decades that followed, there were dramatic declines in birth rates in some less developed countries, somewhat more gradual declines in others, and almost no decline in still others. Nonetheless, the total fertility rate (TFR) in less developed countries declined from about 6.0 in the early 1950s to about 2.5 today, a much more rapid decrease than that of Europe and North America. As impressive as that decline may be, there is still a long way to go. Global population is at an important crossroad. Will the world continue on to "zero population growth" or not?

Most Populous Countries, 2010 and 2050

2010 2050
Country Population (millions) Country Population (millions)
China 1,338 India 1,748
India 1,189 China 1,437
United States 310 United States 423
Indonesia 235 Pakistan 335
Brazil 193 Nigeria 326
Pakistan 185 Indonesia 309
Bangladesh 164 Bangladesh 222
Nigeria 158 Brazil 215
Russia 142 Ethiopia 174
Japan 127 Congo, Dem. Rep. 166

Source: Carl Haub, 2010 World Population Data Sheet.


Youth Dependency

In most of the world, falling fertility has led to changes in the age structure of the population. There are 2.4 adults of working age (15 to 64 years) for every child under age 14. By 2050, the United Nations estimates that there will be 3.3 adults of working age for every child.

But there are large differences between the age structure of populations in more developed and less developed countries. In more developed countries, children under 14 make up only 17 percent of the total population, and there are 4.1 adults of working age for every child under 14. As a result, youth dependency—the number of children economically dependent on the working-age population—is relatively low.

The cost of providing for the needs of young people, particularly education and health care, is distributed over a large number of working adults. However, in less developed countries where child survival has improved and fertility remains high, youth dependency is significantly greater. In sub-Saharan Africa, young people make up more than 42 percent of the total population, and there are only 1.3 working-age adults for every child under 14. In countries such as Uganda, where a woman has on average more than six children, there is a 1-to-1 ratio of working-age adults and children under 14. This high youth dependency burdens governments, communities, and families as they try to meet the needs of large, young populations.

Old-Age Dependency

Improved health, increased access to education, and economic growth have led to lower fertility rates and longer life expectancy in every region and across socioeconomic groups. The world's population is growing older. While this shift represents a major global success story, aging populations also present challenges to families, communities, and countries. This demographic shift is unprecedented in world history, and is most likely irreversible.

Not only is the world's population becoming older, the older are living longer. Those ages 80 and older are the most rapidly growing age group worldwide. To maintain current standards of living in more developed countries and to improve prospects for those in less developed countries, countries must include and involve older populations as productive and active contributors to society.

Gender, Employment, and Dependency

Women are essential to a demographic dividend—the potential of a large cohort of youth to provide a boost to economic growth. The advantage of a larger working-age population supporting a smaller proportion of dependent children and the elderly can only be realized if a greater supply of labor is productively employed.

Among the Asian "tigers" such as Hong Kong, South Korea, Singapore, and Taiwan, high levels of female educational attainment and rapidly increasing female labor force participation contributed to rapid economic growth. According to the International Labour Organisation, while women in these countries were subjected to poor working conditions and lower wages, the economic expansion ultimately lifted most households out of poverty.

Despite the youthful age structure of many developing countries, a demographic dividend is unlikely to occur for a variety of factors, including poor educational preparation of the workforce and a lack of decent employment options. In a majority of countries, women are more likely to be unemployed than men. In addition, the effect of an imbalanced sex ratio resulting from son preference, as seen in a number of Asian countries including China, may portend a shortage of women for jobs typically occupied by women.

Improved Sanitation

An estimated 1.5 million deaths are caused by diarrhea each year, largely due to a lack of clean drinking water, poor sanitation and hygiene, and poor nutrition and health. Improving sanitation is just one of a comprehensive set of solutions needed to reduce diarrhea deaths, but it is a proven method that should remain part of diarrhea prevention strategies.

Recognizing the importance of basic sanitation, world leaders committed to the Millennium Development Goal (MDG) target of halving the percentage of the world's population without access to basic sanitation from 46 percent in 1990 to 23 percent in 2015. The most recent data from the WHO/UNICEF Joint Monitoring Programme for Supply and Sanitation (JMP) indicate that progress in meeting this goal is insufficient, and today more than 2.6 billion people, or approximately 39 percent of the world's population, still do not use improved sanitation facilities.