At the other extreme, scan now for nations with very low rates of increase. What region of the world are they concentrated in?
Europe -- in fact for Europe as a whole, r% = 0.0%
Eighteen individual nations in Europe actually have negative per capita rates of growth: Belarus, Bosnia-Herzegovina, Bulgaria, Croatia, Estonia, Germany, Greece, Hungary, Italy, Latvia, Lithuania, Moldova, Poland, Portugal, Romania, Russia, Serbia, and Ukraine
What does that mean for their populations? Yes, that they are shrinking (d>b).
Operationally the United Nations (UN) defines nations that have rates of natural increase less than or equal to 0.2% to be at "zero population growth" (ZPG) That is, when r is less than or equal to 0.002, the nation is considered to have stopped growing.
All of Europe, and 32 nations within it are at ZPG, by this definition as are Japan and Georgia.
East Germany was the first to reach ZPG (in 1969), with West Germany next (in 1972).
On the face of it, it sounds like quite a few nations have stable populations, doesn't it? It is interesting (and instructive) to look at it from the perspective of the percentage of the global population that these nations represent.
Let's be generous and allow that all of Europe has stabilized (even though some individual nations within Europe have r % > 0.2%). In that case, the percentage of the world's population that is stable is about 13% (summing Europe overall plus Japan's population).
In fact, in 2008 for the first time, r for the 'more developed world' overall was 0.2% [now, in 2013, it is 0.1%), so squeaked in under the ZPG definition! This totals to ~ 18% of the world's pop.
So, between 13 and 18% of the world's population has stopped growing, depending on how you figure it.
Thus, by comparing r's across the globe, we can see that progress has been very uneven at halting population growth. Some nations are at ZPG while others still have rates > 3.0%.
This translates into a difference in doubling times of about 20 versus about 300-400 years for r (%) = 3.0 versus 0.2%.
Now, these differences in percentages sound deceptively small. For example, 1% and 3% both sound small, and not that different from each other. People commonly get fooled by these deceptively small differences! It is important to remember that, because the rate of natural increase functions like compound interest, these differ by a factor of 3 only in the first year.
What happens to that apparently small difference over 100 years?
|Pop growth rate per year (r%/yr)||Pop growth rate per century (%)|
Over a century, one basically triples, while the other increases over 19 fold!
By the same token, when shopping for a bank, it makes sense to choose the one that gives 1% more interest! The interest itself earns interest, just as children bear children -- both are compounding phenomena.
Similarly, "small" differences in assumptions about what will happen to r (and assumptions about other parameters, that we'll discuss later) over time yield population projections for the year 2050 ranging from about 7 billion to over 13 billion! The uncertainty between these estimates (~ 6 bill) is huge, considering our current population of about 7 billion!
Uncertainty about changes in r result more from uncertainty future behavior of fertility rates than about uncertainty concerning death rates, although death rates are becoming increasingly difficult to predict as the AIDS epidemic takes its toll.
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Page maintained by Patricia Muir at Oregon State University. Last updated Nov. 14, 2013.