Experience from 83 countries shows that a 15% increase in contraceptive availability decreases fertility by nearly one child per woman. Birth rates have fallen two to seven times faster in lower-income countries with effective family planning programmes than they did in Europe and North America during a similar transition from high to low fertility. The rate of contraceptive use in developing countries rose from 40% in 1980 to 49% in 1990. At present, 15% of people in lower income countries use natural and barrier methods, as against 50% in upper-income countries.
Another source estimates that access by fertile couples to contraception has grown from under 10% three decades ago to more than 55% currently, in the developing world. This has helped reduce the historical average of 6 children per family (in virtually all societies) to about 3.8 in the developing world. Still, United Nations estimates put the number of women who want fewer children but have no access to family planning at 500 million.
A Sino-American project sponsored by China's State Family Planning Commission and the Rockefeller Foundation has introduced new contraceptive methods into rural areas. The project covered 16 experimental townships with a total population of 360,000 and 75,000 women of child-bearing age. By telling women about contraceptive methods available, doctors and family planners involved in the project were able to help them make a better choice. Figures from the experimental area between 1992 to 1997 show that the programme did not mean a change in the use of previous methods or an increase in the number of unplanned pregnancies or abortions, meaning that informed choice can be introduced in more rural parts with a good family planning record. The Family Planning Commission has also had informed choice projects in 21 other counties in China, which is the world's most populous nation, with over 1.2 billion people. It started a family planning policy to control population growth at the beginning of the 1980s. In recent years, family planning workers have worked hard to provide quality service to improve the health of mothers and babies and to combine family planning with improved living standards in rural areas, which hold most of the country's population.
There is a large – and growing – unmet demand for family planning. Many people in the developing world who want a smaller family are too poor to afford the full cost of modern methods. Subsidized programs of family planning can reduce fertility.
Motivation, rather than differential access to modern contraception, is the primary determinant of fertility. Individuals respond to scarcity by having fewer children, and to perceived opportunity by having more children. Contrary to the demographic transition model, economic development does not cause family size to shrink; rather, at every point where serious economic opportunity beckons, family size preferences expand (Abernethy's Axiom).