Fertility Falls, Population Rises, Future Uncertain

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Although the average woman worldwide is giving birth to fewer children than ever before (see Figure 1), an estimated 136 million babies were born in 2007.1 Global data do not allow demographers to be certain that any specific year sets a record for births, but this one cer­tainly came close. The year's cohort of babies propelled global population to an estimated 6.7 billion by the end of 2007. (See Figure 2.)

The seeming contradiction between smaller-than-ever families and near-record births is easily explained. The number of women of childbearing age keeps growing and global life expectancy at birth continues to rise. These two trends explain why population continues growing despite declines in family size. There were 1.7 billion women aged 15 to 49 in late 2007, compared with 856 million in 1970. The average human being born today can expect to live 67 years, a full decade longer than the average newborn could expect in 1970.

Only the future growth of the reproductive-age population is readily predictable, however: all but the youngest of the women who will be in this age group in two decades are already alive today. But sustaining further declines in childbearing and increases in life expectancy will require continued efforts by governments to improve access to good health care, and both trends could be threatened by environmental or social deterioration. The uncertain future of these factors makes population growth harder to predict than most people realize.

Diversity in fertility rates (the average number of children born to each woman) and life expectancy (the years that the average baby born today can be expected to live) marks the world's population in the early twenty-first century. Women typically bear five or six children in parts of sub-Saharan Africa and western Asia, while women have fewer than two in most industrial countries and some developing ones, such as Cuba, Sri Lanka, Thailand, and Tunisia.

Fertility rates that were consistently below two children per woman would eventually lead to a shrinkage of national populations in the absence of counterbalancing immigration. It can take decades for low fertility to halt growth, however, in populations with large proportions of young people due to high fertility in the past.

Life expectancy worldwide varies from a high of 83 years in Japan to a low of 40 years in Swaziland, the country with the highest prevalence of HIV infection. Worldwide, deaths from AIDS totaled approximately 2.1 million in 2007, and even more people—some 2.5 million—are estimated to have been newly infected with HIV that year.2 One bright sign is that in 2007 the Joint United Nations Programme on HIV/AIDS and the World Health Organization lowered their estimates of HIV infections worldwide, from approximately 39 million to 33 million.3 But this represented a statistical adjustment, not a downward trend in infections.

Due to both the unprecedented number of people alive and the ease of travel, the global movement of people has continued on the largest scale in history. Data are insufficient, however, to be confident about trends from one year to the next. The United Nations estimated that in 2005 nearly 200 million people lived outside their country of birth, a "nation" of international migrants as large as Brazil—and twice as many people as were in that category in 1980.4

U.N. demographers believe that the numbers of people moving to other countries to work and live is rising, propelled by increases in undocumented international migration and in refugees returning to their home countries.5 Many more people move within countries. By the end of 2008, half of the world is expected for the first time in human history to live in such urban areas—though since the definition of "urban" varies by country, there is no way to be certain when this moment of global rural-urban equilibrium actually occurs.6

The United States adds to global demo­graphic diversity by having by far the largest population in the industrial world (about 303 million) and average fertility above two child­ren per woman, the highest among industrial countries.7 In 2006, U.S. fertility rose to its highest rate since 1971—2.1 children per woman.8 Among the reasons for the jump may be decreasing access to abortion and greater proportions of young people lacking easy and affordable access to sexuality education and contraception. Although this level of fertility could eventually stabilize an industrial country's population if there were no net immigration, in the United States the proportions not only of immigrants but of young women of childbear­ing age are both so high that no such outcome is imminent.

Among the most direct influences on fertility is access to and use of contraception. More than 700 million women, half of those aged 15 to 49 in developing countries, are at risk of unin­tended pregnancy, due to either improper use of contraception or—for an estimated 137 million women—no use of contraception at all.9 At the same time, spending on family planning by governments worldwide has been stagnant in recent years—and has remained at a fraction of what governments agreed is needed to assure all women and couples access to services and contraceptives.10

A trend that may be more hopeful for the future of world population is the gradual improvement worldwide of women's health and their economic, educational, and political status relative to men. For the past two years the World Economic Forum (WEF) has assembled a global index of the closing of this gender gap. The 2007 index showed slight improvements over 2006 in every category except health.11 A comparison of the percent of the overall gender gap that had closed and the fertility rates of 128 countries indicated a clear correlation between high female status and low fertility.12 (See Figure 3.) The new WEF index could provide a dataset worth watching in the years ahead, and—if the gender gap continues narrowing—could point the way toward a more environ­mentally sustainable and socially equal human pop­ulation in the years ahead.

  1. Unless otherwise noted, all demographic data are from Population Division, Department of Economic and Social Affairs, World Population Prospects: The 2006 Revision (New York: United Nations, 2008).

  2. Joint United Nations Programme on HIV/AIDS and World Health Organization, AIDS Epidemic Update 2007 (Geneva: 2007).

  3. Ibid.

  4. Population Division, Trends in Total Migrant Stock, The 2005 Revision (New York: United Nations, 2006).

  5. U.N. Population Division director Hania Zlotnik, quoted in U.N. Department of Public Information, Press Conference on International Migration and Development, press release (New York: 4 April 2006).

  6. Population Division, Department of Economic and Social Affairs, World Urbanization Prospects 2007 (New York: United Nations, 2008).

  7. Population size from U.S. Census Bureau, U.S. POPClock Projection, available at www.census.gov/population/www/popclockus.html, viewed 29 January 2008; fertility rate from Population Division, op. cit. note 1.

  8. Brady E. Hamilton, Joyce A. Martin, and Stephanie Ventura, "Births: Preliminary Data for 2006," National Vital Statistics Reports, 5 December 2007, pp. 1-18.

  9. Susheela Singh et al., Adding It Up: The Benefits of Investing in Sexual and Reproductive Health Care (New York: Alan Guttmacher Institute, 2003).

  10. J. Joseph Speidel, "Population Donor Landscape Analysis for Review of Packard Foundation International Grantmaking in Population, Sexual and Reproductive Health and Rights," Presented at task force of The David and Lucile Packard Foundation, 6 September 2006.

  11. Ricardo Hausmann, Laura D. Tyson, and Saadia Zahidi, The WEF Global Gender Gap Report 2007 (Geneva: World Economic Forum, 2007).

  12. Ibid.