This article is excerpted from the forthcoming Population Bulletin "The Demographic Divide."

(December 2005) Public attention has begun to focus on the "demographic divide," the vast gulf in birth and death rates among the world's countries. On one side of this divide are mostly poor countries with relatively high birth rates and low life expectancies. On the other side are mostly wealthy countries with birth rates so low that population decline is all but guaranteed and where average life expectancy extends past age 75, creating rapidly aging populations.

But this gulf is not a simple divide that perpetuates the status quo among the have and have-not nations. Rather, it involves a set of demographic forces that will affect the economic, social, and political circumstances in these countries and, consequently, their place on the world stage. Demographic trends are just one of the factors determining the future of these countries, but these trends are a crucial factor.

No Global Birth Dearth: The Reality of Different Population Growth Patterns

As average population growth slowed globally over the last century, the range of national demographic experiences actually widened. Growth rates have remained high in many countries such as Burkina Faso, Chad, and Iraq, while they have plummeted in others including Italy, South Korea, and Thailand.

Many other countries are poised at the edge of these extremes—some (such as Germany and Hungary) are on the verge of population decline because of sinking fertility rates, while others (including Cambodia and Nicaragua) could rise into the higher extreme if health conditions improved and death rates fell. Immigration is the wild card: It can hasten or slow these trends.

Despite media reports about population decline and a global "birth dearth," less than 15 percent of the world's population lives in countries that are projected to lose population between 2005 and 2050. Taken together, these countries account for just under 1 billion people. By 2050, these countries will account for less than 10 percent of global population. The media attention and concern arise because the countries slated for decline are among the wealthiest and most influential, including Japan, Germany, Italy, and Russia. Europe is the only continent projected to lose population (70 million) by 2050 (see figure).

Projected Population Increase or Decrease by Country or Region, 2005-2050

Source: Carl Haub, 2005 World Population Data Sheet.

Another group of countries (including Iran and Australia) is still growing in population, but very slowly—a projected increase of 1 percent annually between 2005 and 2050. Some of these countries are projected to fall into annual decline by 2050. With its 1.3 billion people, China is the most demographically important in this group: After decades of stringent government controls on childbearing, the Chinese fertility rate has fallen so low that deaths will outnumber births by 2035. Even so, China is projected to add at least another 130 million people by then: Its projected size will be 1.4 billion in 2050.

A third group of countries will grow at a more modest rate, but will add the largest number of people to the world. The United States is in this group: It is projected to increase 42 percent between 2005 and 2050, adding more than 100 million people. Such demographic giants as Bangladesh, Brazil, India, and Indonesia are also in this moderate growth group. Many of these countries have had impressive fertility and mortality declines, but still have considerable momentum for future growth thanks to a young age structure and moderately high fertility, and—for the United States—immigration.

The Correlation Between High Population Growth and Lagging Development

The countries on the high-growth side of the demographic divide, such as Madagascar, Mali, and Yemen, account for just 8 percent of world population in 2005. However, these countries are slated to double or triple in size and their global share will rise to nearly 20 percent by 2050. As a group, these countries' aggregate population will swell from 0.7 billion to 1.9 billion between 2005 and 2050, even assuming a decline in fertility.

Except for a few petroleum-exporting countries that have enjoyed substantial economic growth in the last half century, nearly all the high-growth countries are included on the United Nations' list of least developed countries. The countries on this list have the world's lowest per capita income and literacy levels, and their economies tend to rely heavily on agriculture rather than industry or manufacturing.

The few least developed countries that do not have rapidly growing populations tend to have high mortality or heavy emigration of residents seeking jobs. Most of the high-growth countries are in sub-Saharan Africa, where fertility has remained high and mortality has declined enough to fuel rapid population growth. Outside Africa, the countries at this extreme of the demographic divide include some of the most impoverished: Afghanistan, Bhutan, Guatemala, and Haiti.

Consequences of the Demographic Divide: Japan Versus Nigeria

What is worrisome about the demographic divide is not the differences among nations' population growth rates, but the disparities associated with these demographic trends—disparities in living standards, personal health, well-being, and future prospects.

People in countries on the extremes of the divide have starkly different lives today and face very different futures, as illustrated by a comparison between Japan and Nigeria, two countries of similar population size in 2005 (see table).

The Demographic Divide: Nigeria and Japan

Population (millions)
Lifetime births per woman
Annual births (millions)
Annual deaths (millions)
Life expectancy at birth (years)
Infant deaths per 1,000 births
Adults with HIV/AIDs, 2003 (%)
Percentage of population living on <US $2/day
GNI PPP per capita*

NA=not available or not applicable.
*GNI PPP = gross national income in purchasing power parity divided by population.
Sources: Carl Haub, 2005 World Population Data Sheet; and United Nations Population Division, World Population Prospects: The 2004 Revision (2005).


Japan has the world's second-largest economy and enjoys a high per capita income (PPP)—US$30,040 in 2003. Japanese people are highly educated: Most finish secondary school and at least one-third go on to college or university. The Japanese are also healthy: They have the world's longest life expectancy—82 years—and among the lowest rates of infant mortality. And the Japanese have a high standard of living, with access to all the trappings of the modern information age.

At 1.3 children per woman, Japan also has one of the world's lowest total fertility rates (TFR). Given the low mortality at older ages in Japan, this TFR means that the country has one of the most rapidly aging populations in the world. Japan's population has seen considerable changes since the end of World War II, which left its economy in shambles. Its TFR was above 4.0 in the 1940s, but fell below 3.0 by 1952 and below 1.5 by 1995. Life expectancy in Japan rose from about 64 years in the 1950s to an unheard-of 80 years by the late 1990s.

Japan has achieved impressive economic growth and improvements in health, but it is still transitioning from a patriarchal society to a more gender-equal society. Japanese women have felt squeezed between their traditional roles as homemakers and their wish to participate fully in the economy and modern society. Japanese women wait until their late 20s to marry—and many may choose to remain single.

The mean age at first marriage for women in Japan rose from 23.0 in 1950 to 27.8 in 2004.1 Women there have their first child at age 28.9 on average. Demographers have known that Japan was headed for population decline, but early reports for 2005 indicate that Japan experienced more deaths than births and was officially declining in terms of population—two years ahead of projections.2


While Nigeria's fertility and mortality rates have also declined since 1950, Nigeria remains a high-fertility, high-mortality country: Its women have 5.9 children on average, and Nigerians have a life expectancy from birth of just 44 years. The country's population has increased fourfold since 1950, when it contained barely 33 million people.

In 2005, Nigeria 's 132 million people made it the most populous country in Africa. While it is a petroleum-exporting country, Nigeria's per capita income is about one-half the average for sub-Saharan Africa (US$930, compared with an average of US$1,830 for the region as a whole). Some 91 percent of Nigerians live on less than US$2 per day.

Only about one-half of Nigerian women are literate. About 5 percent of Nigerians completed education above high school.3 Nigerian women marry and have children at young ages—on average before age 20.4 Nigeria 's population is projected to reach 258 million by 2050, and, with 27 percent of its population still below age 15, the country will have considerable momentum for growth in the second half of the 21st century.

Mary Mederios Kent is editor of the Population Bulletin series at the Population Reference Bureau (PRB). Carl Haub is PRB's senior demographer and holds its Conrad Taeuber Chair of Population Information.


  1. Statistical Bureau and Statistical Research and Training Institute, Statistical Handbook of Japan, accessed online at, on Nov. 13, 2005.
  2. Leo Lewis, "Decline in Population Sparks Fears for Economy," The Times (London), Aug. 24, 2005.
  3. UNESCO Institute for Statistics, "Statistics in Brief," accessed online at, on Nov. 13, 2005.
  4. National Population Commission (Nigeria) and ORC Macro, Nigeria Demographic and Health Survey 2003 (Calverton, MD: National Population Commission and ORC Macro, 2004), accessed online at, on Dec. 16, 2005.