These pages show the age-sex pyramids of actual countries. I have chosen the countries to show the basic forms the pyramid can take. The first pyramid is the typical pyramid where the sides gradually slop in toward the center and eventually fade away. Each bar in the pyramid represents a 5 year age group, males on the left and women on the right.
As you look at this pyramid notice how the age cohorts grow steadily smaller as they age. Notice also that there are typically fewer men in any given age group, especially in the older ages. Finally notice that the pyramid seems to suddenly expand outward in the last age group. This is because it is open (every one over the age of 80). Keep in mind also that the age-sex pyramid reflects quite clearly the 'demographic experience' of the population represented in it. Note any peculiarities in this first one and see if you can figure out what might have happened in Argentina to create that peculiarity.
The basic demographic data for Argentina show a crude birth rate of 20, a crude death rate of 8 and a rate of natural increase of 1.2 percent per year. Infant mortality is moderately high at 19 infant deaths per 1000 births. Life expectancy at birth is pretty high at 74 years. The total fertility rate is 2.7, that is if current age specific birth rates hold, each woman will bear, on average, 2.7 children during her reproductive years.
Figure 1
Typical Pyramid: High Death, High Birth rate
The next pyramid is for Kenya and is very typical of what is happening in a country where there have been dramatic changes in the birth and death rates, but most especially in the death rates. This pyramid is obvious expanding -- the younger age cohorts are much, much larger than the older cohorts (unlike the pyramid above where each younger cohort is only a little bit larger than the one that preceded it). Notice also that in this pyramid there does not seem to be the imbalance between men and women noted in the one above.
Notice the general shape of this pyramid and see if you can explain what is happening in the younger age groups -- how do these differ (the age groups from 0-4 through 10-14) from the age groups right above them (15-19 to 30-34 for example)?
The essential demographic data for Kenya show a picture quite different from that of Argentina. First the crude birth rate for 1998 is 32 and the crude death rate is 14. The rate of natural increase is about 1.7 percent per year, not too bad in this day. The infant mortality rate is 59 per thousand live births. The high infant mortality also means a relatively low life expectancy at birth, only 47 years. The total fertility rate is 4.1, that is, each woman can expect to have about 4 children during her child bearing years.
Figure 2
Expanding Pyramid: Low death rate, high Birth rate
Finally we come to the 'stable' pyramid. Such a pyramid tends to have relatively straight sides and tapers in gradually at the top. This one for Canada shows that pretty much except for the so-called baby boomers (25-29 through 45-49). If we take them down a bit, we would indeed have the straight sided pyramid that is typical of a stable population. Incidentally, such population pyramids probably do not exist in the wild, but only as a consequence of projections based upon certain assumptions (birth and death rates are low and nearly equal).
The demographic data for Canada reflect the nature of the pyramid. First of all the crude birth and death rate are 12 and 7, respectively, per thousand population. The rate of natural increase is very low -- only 0.5 percent per year. Infant mortality is quite low: only 6 per thousand live births. Life expectancy at birth is fairly high at 79 years. The total fertility rate is also correspondingly low -- only 1.7 children per woman.
Figure 3
Stable Pyramid: low death and birth rates
All of the data and the pyramids are generated from the International Data Base at the U.S. Census. You should go there and explore other countries.
Copyright © 1996, 1997, 1998, 1999, 2000 by Richard H. Anderson, the Department of Sociology and the University of Colorado at Denver.
This page last revised: November 15, 2000. Please contact Richard H. Anderson (randerso@carbon.cudenver.edu) if you experience any problems or have comments about these pages.