As this table makes clear, the rate of population growth peaked sometime in the early 1970s and has been declining ever since. Another way of looking at this data is by examining the average annual rate of population growth which is captured on this table (2):
he rate at which the world's population has been increasing every year has been gradually declining since the early 1970s and will likely continue to decline through the beginning of the 21st century and beyond.
Although the rate of population growth is slowing due to the age structure of the population and the beginning absolute population levels, the world's population will probably to grow through the middle of the 21st century, although the growth will keep getting smaller and smaller. By 2045-50, for example, the United Nations estimates that annual average rate of population growth will decline to 0.34 percent (3).
This decline is reflected in the increasing length of time it takes to add another billion people to the world's population (4):
Based on the median variant (often viewed as the most likely scenario) of the United Nations' population projections, world population would peak at somewhere under 10 billion in the latter half of the 21st century and then gradually begin to declined.
The main factor driving the slow down in the rate of population growth is the worldwide decline in |total fertility rates|. The total fertility rate measures the average number of children born to women during their child bearing years. A TFR of 2.1 is considered the replacement level -- at that rate a population would neither grow nor decline.
TFRs have declined dramatically around the world over the last two decades (5):
Total fertility rates around the world have declined by 33 percent just since 1985, and both United Nations and US Census Bureau projections expect them to decline further. By 2025 the US Census Bureau estimates that the TFR of the less developed countries will have fallen to 2.4 -- very close to the replacement level.
Should the decrease in total fertility rates stop, however, the United Nations projects world population in 2040-50 could reach as high as 11.9 billion. On the other hand if the decline in total fertility rates should accelerate, world population could plateau at 7.9 billion by 2040-2050 (6).
One of the main consequences will be a shift in where the world's population lives. Eighty-eight percent of population growth from 1990-1995 occurred in Asia and Africa, and this trend will only continue. By 2050 Africa's population is expected to triple while Europe's is expected to decline by 7 percent by 2050 (7).
Footnotes:
1. McDevitt, Thomas M. World population profile: 1998. Washington, DC: U.S. Government Printing Office, 1999, p.A3.
2. McDevitt, Thomas M. World population profile: 1998. Washington, DC: U.S. Government Printing Office, 1999, p.A4.
3. United Nations. The 1998 revision of the world population estimates and projections. New York: United Nations, 1999.
4. United Nations. The 1998 revision of the world population estimates and projections. New York: United Nations, 1999.
5. McDevitt, Thomas M. World population profile: 1998. Washington, DC: U.S. Government Printing Office, 1999, p.A39.
6. United Nations. Concise report on the world population situation in 1995. New York: United Nations, 1995, pp.1-2.
7. United Nations. Concise report on the world population situation in 1995. New York: United Nations, 1995, pp.5-6.
