The current rate of natural increase (%) is now lower than its historical high of a bit over 2% which held until about 1970, as indicated on the diagram below (now, as of mid-2008, the rate is ~ 1.2%):
Figure 1
(The precipitous drop in 1960 was the result of the massive famine that occurred in China at around the time of the "Great Leap Forward." A figure similar to this, but running through more recent times than the figure above will be given in lecture as a handout.)
The difference between the current r and its historical high doesn't sound like much. However, when multiplied by N (the number in the population), this apparently small difference translates into a huge difference in numbers of people added per year:
Recall: G = r*N where r is not a percent (Click on "G " to review notes on this calculation.)
So, for the current global population of approximately 6.7 billion, at the historical high r of about 2.1%:
G = 6.7 Bill * 0.021 = 141 million persons
Whereas for the current global population of ~ 6.7 billion and the current r of ~ 1.2 % (0.012):
G = 6.7 Bill * 0.012 = 80 million persons
This "small" difference in r translates into a difference of ~60 million people gained per year!
This decrease in the global r has resulted largely from a decrease in the average number of children born per woman ("TFR" ) from about 5 to about 2.6 children per woman. Without this decrease, the world population in 1996 would have been about 6.2 billion rather than 5.7 billion people – a difference of nearly one half a billion!
Now, the media commonly imply that since r has decreased since 1970, that means we are adding fewer people to world now than we were then.
Check yourself #2: Is that necessarily true? That is, since r is lower now than in 1970, is G necessarily smaller? (Click on Answers to check yourself.)
While r (the rate of net reproduction per individual) has decreased slightly, as we just saw, what has happened to "N" (the number in the population)?
Figure 2
As you can see in the figure above, the number of people (N) in the global population has continued to increase. (Project this out to mid-2008, when we're over 6.7 billion.....)
And the consequence of this larger N, despite a slightly decreased r, has been, until very recently, a generally increasing G, as illustrated below for the global population. (The figure illustrates the annual net addition to the global population over the period 1950 - 1994; a similar figure illustrating the trend through more recent times will be given as a handout in class.):
Figure 3
Believing that G will drop as much or as fast as r declines represents a basic confusion between per capita rates of growth (r) and absolute growth for the whole population (G).
It all adds up to a continued increase in the size of the human population: While r is somewhat lower than its historical high, N is way up, so the drop in G (the number gained per year) is not as great as would be implied by the decrease in "r."
The global r increased from the 1950's through the early 1970's (see Figure 1, above), then decreased until the early 1980's. The decrease was largely because of family planning programs, examples of which we'll explore more later. (Click here on Patterns to jump to that point in the notes, if you wish.)
However, the decrease in r basically plateaued through the 1980's (Figure 1, above). There are several reasons for this plateau, which are listed briefly here. All will be discussed more later in these notes; click on highlighted words below to jump to those sections now, if you wish.
1. Fertility declines in the "demographic giants" of India and China (nations with huge populations), which had been rapid, stalled. In India, family planning programs decreased after the defeat of National Congress Party, which had been criticized for enforcing birth control and sterilization too harshly. China 's policies also relaxed somewhat.
2. Changes in population age structures gave greater absolute birth rates.
3. Finally, until very recently, few additional nations made significant fertility declines since the 1970's.
In the developing world overall, r has been fairly steady for the last 30 years or so at close to 2% (it is 1.8% for the nations of the developing world overall excluding China). Both fertility and mortality have decreased, resulting in fairly stable rates of natural increase (r).
In the next two sections, we will look at some regions of the world that represent dramatic contrasts in terms of current growth rates.
(To move to the next section in these notes (on areas of the world experiencing rapid population growth), click the box at the bottom of the page labeled ">>." To return to the previous section, click the box labeled "<<" and to return to the master directory for the BI301 web site, click the box labeled "CONTENTS.")
