The choice of voluntary family planning programs as the principal policy instrument is based largely on the documentation of a substantial unsatisfied demand for contraception. In surveys, large proportions of married women in the developing world report that they do not want a pregnancy at the time of the interview. Some of these women want no more children because they have already achieved their desired family size, while others want to wait before having the next pregnancy. A substantial proportion of these women (more than one-half in some countries) risk pregnancy by not practicing effective contraception (including sterilization), and, as a result, unintended pregnancies are common. In 2008, 30 million births (out of a total of 123 million) were the result of unintended pregnancies, and an additional 30 million pregnancies ended in induced abortions (Singh et al. 2009).

Why do apparently motivated individuals fail to practice contraception? The answer lies in a mixture of social and health service-related reasons. In the past, a lack of access to services or information was a dominant obstacle. But access in the geographic sense has improved with the implementation of family planning programs and the expansion of the role of private-sector providers. These efforts have not eliminated all unmet need, however, because many service points still offer too few methods and little if any information, or they are otherwise deficient in quality. In addition, other factors—such as fear of side effects of contraceptive methods and overt or suspected disapproval of husbands/partners and other family members—are significant barriers to use in many societies.

The existence of this unmet need for contraception was first documented in the 1960s, and it convinced policy makers that family planning programs were needed Page 2456  |  Top of Articleand would be acceptable and effective. The health and human rights benefits of family planning and reproductive health programs have provided additional rationales for this policy approach, which was endorsed at the 1994 United Nations International Conference on Population and Development. The program of action adopted by the participating governments encourages the expansion of reproductive health and family planning programs as a means to improve women's reproductive freedom and health. Coercion of any kind is strongly opposed.

Since the early 1960s, large changes in reproductive behavior have occurred in most of the developing world. Around 1960, only a tiny fraction of couples practiced contraception, and knowledge of methods was very limited. In contrast, contraceptive knowledge is now widespread and more than one-half of married women in the developing world are current users of contraception. The large majority of these users rely on modern methods, including male and female sterilization, the IUD, and the pill.

As a consequence of this widespread adoption of contraception, birth rates have declined sharply. In the past, fertility was high and relatively stable at over 6 births per woman. Since a precipitous decline began in the 1960s, the fertility of the developing world has been reduced by more than one-half, reaching 2.7 per woman in the period from 2005 to 2010 (United Nations 2011). The largest fertility declines occurred in Asia and Latin America and the smallest in sub-Saharan Africa. On average, the pace of change in reproductive behavior in the developing world has been faster than was the case in Europe and North America in the late nineteenth and early twentieth centuries.

A key factor contributing to this rise in contraception has been the diffusion of information about and access to contraceptive methods, aided by a rapid expansion of family planning programs. Experiments have provided the most direct and convincing evidence of the value of well-designed family planning services. An example of a large and influential experiment is the one conducted in the Matlab district of rural Bangladesh (Cleland et al. 1994). When this experiment began in the late 1970s, Bangladesh was one of the poorest and least developed countries, and there was considerable skepticism that reproductive behavior could be changed in such a setting. Comprehensive family planning and reproductive health services were provided in the treatment area of the experiment. A wide choice of methods was offered, the quality of referral and follow-up was improved, and a cadre of well-trained women replaced the traditional birth attendants as service providers. The results of these improvements in the quality of services were immediate and pronounced, with contraceptive use rising sharply. No such change was observed in the comparison area. The differences between these two areas in contraceptive use and birth rates have been maintained over time. The success of the Matlab experiment demonstrated that appropriately designed services can reduce unmet need for contraception even in very traditional settings with low levels of development.

Evidence from poor African countries confirms that a commitment to family planning in such settings can be successful. For example, Rwanda's fertility had been one of Africa's highest in the twentieth century, remaining above 6 births per woman until 2005 (NISR 2012). But in the early twenty-first century the government renewed its lagging commitment to family planning and, with strong support from international donors, sharply increased access to contraceptive methods throughout the country. In addition, a countrywide information program was implemented. Large changes in reproductive behavior resulted: the use of modern methods of contraception rose from 10 percent in 2005 to 45 percent in 2011 (Singh et al. 2009; NISR 2012).

Despite the undoubtedly crucial role of family planning programs, they are not the only or even the principal cause of changes in reproductive behavior in the developing world. Instead, socioeconomic change is considered by most analysts to be the dominant driving force of the fertility transition. As traditional agricultural societies are transformed into modern industrial ones, the cost of children (e.g., for education) and a decline in their value (e.g., for labor and old-age security) to parents leads to declines in desired family size. In addition, with fewer children dying at young ages, fewer births are needed to ensure the survival of the number of children that parents desire. A rise in human development and, in particular, improvements in health and education appear to be the principal determinants of progress through the fertility transition (Jejeebhoy 1995; Sen 1999; Cleland 2001). In fact, it is possible for poor populations to reach low fertility levels, provided literacy and life expectancy are high. Well-known examples of this occurred in Sri Lanka and the state of Kerala in India.

The primary role of family planning programs is and has been to reduce unintended births by assisting couples with the implementation of their preferences for smaller families through contraception and abortion. Family planning programs have accelerated fertility transitions, so that, on average, these transitions have occurred about a decade earlier than they would have without the programs. Because small changes in fertility have relatively large effects on long-term population growth, this acceleration of fertility decline attributable to programs probably has reduced the eventual population size of the developing world by a few billion (Bongaarts 1997).

Despite fertility declines, population growth continues at a rapid pace throughout most of the developing world. According to United Nations projections, the expected increase in the population of the developing world as a whole between 2000 and 2050 (from 4.93 to 8 billion) is about the same as the historically unprecedented increase that occurred between 1950 and 2000 (from 1.72 to 4.93 billion). This future growth can be attributed to three demographic factors (Bongaarts 1994).

First, the past decline still leaves average fertility about 50 percent above the two-child level per woman needed to bring about population stabilization. With more than two surviving children per woman, every generation is larger than the preceding one, and as long as that is the case population growth will continue. High fertility can in turn be attributed to two distinct underlying causes: unwanted childbearing and a desired family size above two surviving children. Many couples continue to want large numbers of children, partly because of fears of child mortality and partly because of the need for a sufficient number of surviving children to assist them in family enterprises and support them in old age. In most developing countries, the completed family size desired by women still exceeds two children; in some areas, such as sub-Saharan Africa, desired family size is typically above four children.

Second, declines in death rates—historically the main cause of population growth—will almost certainly continue. Higher standards of living, better nutrition, greater investments in sanitation and clean water supplies, expanded access to health services, and wider application of public health measures such as immunization will ensure longer and healthier lives in most countries. The exceptions will be mostly in sub-Saharan African countries, where the AIDS epidemic is severest.

The third growth factor is what demographers call population momentum. This refers to the tendency for a population to keep growing even if fertility could immediately be brought to the replacement level of 2.1 births per woman with constant mortality and zero migration. As a result of a young population age structure, the largest generation of adolescents in history entered the childbearing years in the first decade of the twenty-first century. Even if each of these young women has or had only two children, they will produce more than enough births to maintain population growth over the next few decades.

Population momentum is the most important of these three factors, contributing about one-half of projected future growth. Further large increases in the population of the developing world are therefore virtually certain.

To be effective, population policies should address all these sources of continuing growth, except declining mortality, by implementing several strategies.