In mid-2005, women around the world had an average of 2.7 children, according to the Population Reference Bureau. That seven-tenths of a percentage point above replacement level may not seem like a lot, but it is contributing to a dramatic population expansion, from 6.4 to 9.2 billion, between now and 2050.
Let’s look at the accelerating momentum of population growth. In the year 1000, there were an estimated 254 to 345 million people on the planet, mostly living agrarian lives. World population grew very slowly in those days. In 1200, 200 years later, there were still only 360 to 450 million people. Move all the way up to the relatively modern world, in 1700, and there were still only 600 to 679 million people sharing the planet.
The first billion was reached, probably, in 1802. But after that we really took off as a species. It took just 125 years to add the second billion, in 1927, and only 34 years to get to three billion, in 1961. Four billion (1974) took just 13 years, and five billion (1987) another 13. We crossed the six billion threshold in 1999, after only 12 years. When will we get to seven billion? How does 2012, just six years away, sound?
If you were to chart human population growth between 1950 and what is projected for 2010, it would look like a steady, unbroken ascent, with no interruption from the birth dearth. This is true despite the fact that the growth rate peaked in the mid-1960s, at 2.2 percent per year (it is now 1.3 percent). World baby booms from that period are still having an effect, leading to a large population of women in their child-bearing years, and thus continued growth. And that growth will continue for several decades more.
The population is growing, but the growth is very uneven. Here’s one way of looking at it: in 1970, Europe had 655 million people. In 2050, it will have
653 million, which means that zero population growth has arrived there. Africa had 357 million in 1970, but it will have 1.8 billion in 2050. Asia, similarly, goes from 2.1 billion to 5.7 billion in that period. That’s a huge redistribution of world population. If you took a snapshot today and reduced the population to 100 people, 57 would be Asian, 21 European and eight African. But that ratio is certain to be dramatically different 50 years hence.
Any look at future population is guesswork, and the world’s principal demographer, the United Nations, admits as much. Its projections see almost every country in the world headed toward below replacement-level fertility, which will certainly lead to a birth dearth. "Total fertility in high-fertility and medium-fertility countries is assumed to converge eventually toward a level of 1.85 children," says the UN Population Division.
But are the world’s high-fertility countries, in Africa, South Asia and the Middle East, really going to experience such dramatic drops in their birth rates? Will, for example, Mali, with a birth rate of 7.1 today, eventually start to look like Poland, where it is 1.2? Population Action International is skeptical. "Poor access to family planning and the low social status of women continue to drive high rates of population growth in most of sub-Saharan Africa, in many countries of the Middle East and in parts of South Asia," says the group. "In many of these countries, most couples still want large families, in part to offset continuing high infant mortality."
Even if the rates do decline, actual numbers will probably continue to go up. Thomas Buettner, the UN’s chief of estimates and projections, notes that in some African countries, 50 percent of the population is below 16 years old, so even if these emerging adults have fewer children than their parents, their countries will continue to grow.
Demography is hardly an exact science. "Anytime you project population ahead 50 years, it’s a wild guess," says Jeff McNicoll, a senior associate at the Population Council. "The UN is modeling its projections for the less-developed countries on what has happened in other parts of the world. In Africa, what will happen is highly contingent on economic and political developments." Indeed.