By the 1970s and 1980s population growth in the industrialized countries had begun to fall significantly. By the 1990s some European leaders were expressing concern that low birthrates threatened national economies by reducing the labor force, the tax base, and the number of consumers. Between 1970 and 1975 China registered the fastest five-year birthrate decline in recorded history. Other countries, especially in Latin America and East Asia, experienced declines in fertility. In 1970 the average Brazilian woman had close to 6 children; by 2005 she had 1.9. In 1970 the average woman in Bangladesh had more than 7 children; in 2005 she had 3.1. Fertility in most of the developing world could fall below the replacement level (2.1 children per woman) before 2100. There were several reasons for this decline in fertility among women in the developing world. As fewer babies died of disease or malnutrition, families needed fewer births to guarantee the survival of the number of children they wanted. Better living conditions, urbanization, and more education encouraged women to have fewer children.

In the early 1960s the introduction of the birth control pill allowed women to take control of their own fertility. Family planning was now truly possible. In the early twenty-first century, more than half of the world’s couples practiced some form of birth control, up from one in eight just forty years earlier. However, male chauvinists, religious leaders, and conservative government leaders in many Catholic and Muslim countries restricted access to birth control methods and abortion because they felt that these violated their core beliefs. Birth control and abortion were most accepted in North America, Protestant regions in Europe, the Soviet Union, and East Asia, which explains why these regions had the lowest birthrates and population growth; however, the issue remains controversial.

The most recent estimates are that the world’s population will grow by a further 50 percent between 2000 and 2050, when it will reach about 9 billion. Over the next century it is then expected to level off at about 10 billion.