During the past year, former President Bill Clinton has been warning audiences that “world's population is projected to grow from 6.5 to 9 billion people by 2050, and almost all of that growth will occur in countries least able economically to support new people.”
The 9 billion figure used by Clinton and many others today is actually one of three projections—low, medium, and high variants--made by the United Nations. The medium variant, of course, is the one most widely used. It assumes that the total fertility rate (TFR), the average number of children per woman, will drop from today’s rate of 2.7 to 2.0 by 2050.
But how reliable is that assumption? Fertility rates have declined sharply in the past half century. Between 1950 and 1955, the average TFR was 5.0, almost twice as high as it is today. But, as any Wall Street analyst will tell you, past trends do not always guarantee future results.
It’s possible that fertility rates will not drop as fast as the medium variant indicates. With the decline in government and NGO support for family planning services in many developing nations, fertility rates in some areas may stabilize well above the “replacement rate.” In other areas, fertility rates may actually increase.
One area of particular interest is India, where fertility rates have been cut in half over the past half century. With a TFR of 3.0 and declining mortality rates, India population is projected to grow under medium variant assumptions from 1.14 billion today to 1.39 billion by 2025 and 1.75 billion by 2050. But how reliable is that projection?
The Population Reference Bureau and the Population Foundation of India last year took a closer look at projections for India (“The Future Population of India: A Long-Range Demographic View”). The study looked more closely at the regional differences in fertility. Fertility is much higher in the northern states than in the southern states. The press release noted that:
The large states of the north, the "Hindi Belt," are key to the future size of India's population. About 40 percent of Indians live in this region. Two northern states, Bihar and Uttar Pradesh, with about 93 million and 188 million people, respectively, are already larger than most of the world's countries. Both states currently have a TFR of about 4.3 children per woman.
Relying on state-based data, rather than national fertility rates, the study developed two alternative scenarios. The first scenario assumed that Indian states with a current TFR above "two children" would decrease to 2.1 and then stabilize. The second scenario assumed the TFR would decline until it reached 1.85 children per woman.
While the results of scenario “B” showed India’s projected population for 2050 (1.75 billion) to be close to the UN’s medium variant projection, scenario “A” showed India’s population rising to 1.83 billion by 2050 and 2.18 billion by the end of the century. Which scenario is more likely? The report noted:
Different users will have different opinions as to the appropriateness of the scenarios as they apply to each state. Some, for example, may feel Scenario A appropriate for Bihar, but not Uttar Pradesh. Over such a long period, many different events may influence population trends. States with low fertility today may become concerned about population ageing and decline and encourage more births. Such a turnaround may seem unlikely today, yet precisely this has happened in some countries of Asia which once advocated lower birth rates. Pressure on the availability of agricultural land may cause accelerated migration to urban areas and result in faster fertility decline. Perhaps, continuing son preference will act to keep fertility somewhat higher. And it may simply be that a TFR as low as 2.1 may never be reached in some states.
Population growth in Africa might also surpass expectations. Seven years ago, the International Institute for Applied Systems Analysis (IIASA) projected that global population would peak later in this century at about 9 billion. That report was seized upon by many to suggest that population growth was not a concern (an interpretation rejected by IIASA itself). A few months ago, IIASA revised its 2001 projections slightly upwards when it took another look at fertility trends.
Because of continued very low fertility or further fertility declines in some regions that already had low fertility, Eastern Europe and the China region are now shown by the POP research as having lower population growth than was projected in 2001. This is offset at the global level by higher anticipated population growth in sub-Saharan Africa.
Africa’s population will almost certainly more than double from its current level of around 740 million. Because of the great longer-term uncertainties surrounding the future speed of fertility decline and the possible new health crises under the very poor development conditions anticipated, the 95 percent range by the end of the century is very broad, from a low 1.1 billion to a very high 3.3 billion. The central 20 percent range is 1.9–2.2 billion by 2100. Two factors will in all likelihood keep Africa at the bottom of world development unless some trends change radically in the near future: continued very rapid population growth together with stagnant or declining educational attainment levels (partly as a consequence of rapidly increasing numbers of children), and the additional environmental and agricultural problems likely to be caused by climate change.
One key point to be taken from these and other studies is that population projections—including UN population projections--are only as good as the assumptions built into them. Many today assume that TFRs everywhere will eventually decline to 2.1, or lower, and that global population will likely stabilize and then begin declining before the end of the 21st Century. Perhaps. But it’s always good to check the assumptions. And it’s important to remember that in many countries in sub-Saharan Africa and in some parts of South Asia, like Afghanistan, women who want fewer children often lack access to modern birth control methods.
