THINKING LAB
Building Age Pyramids
Background
The International Programs Center (IPC) of the United
States Bureau of the Census has created an international
data base to meet the needs of organizations that require
its assistance, and for its own research. The data it
contains come from censuses and surveys done by
individual countries, as well as estimates and projections
provided by the IPC. One of the data sets is extremely
useful for building age pyramids. Demographers use such
pyramids as a tool to help them project population trends.You Try It
1.Using the data in the table, construct age pyramids for
both countries. The age pyramids can be drawn by
hand or by using a spreadsheet program.
2.What do the pyramids indicate about the stage of
demographic transition each country is experiencing?
3.Which country, Canada or Mexico, will grow most in the
next decade? Explain why.
4.Are there any differences in the proportion of males
versus females in each age category? That is, is the sex
ratio (the ratio of the number of males to the number of
females) the same in all age categories? If so, which
age categories differ and is the pattern the same for
both countries? What factors might explain any
differences you see between countries and between
genders? Would these differences have any effect on
population growth? Why or why not?Canada Mexico
Number of
males
(x1000)Number of
females
(x1000)Age
Category
0–4
5–9
10–14
15–19
20–24
25–29
30–34
35–39
40–44
45–49
50–54
55–59
60–64
65–69
70–74
75–79
80 +945.9
1069.7
1062.1
1065.6
1051.8
1087.6
1187.8
1396.9
1332.3
1160.8
1034.1
782.2
615.2
547.9
458.9
339.8
337.1
901.5
1015.6
1013.1
1019.8
1009.1
1059.1
1171.0
1369.3
1318.5
1168.8
1035.6
795.7
644.8
598.7
553.1
481.9
647.1
Number of
males
(x1000)Number of
females
(x1000)
5815.6
5799.8
5690.1
5429.8
5060.5
4569.5
3676.1
3012.8
2382.6
2039.9
1651.6
1333.6
1067.0
800.6
545.2
329.8
252.35580.2
5573.9
5478.6
5269.5
4999.2
4620.3
3988.2
3401.6
2741.6
2311.1
1845.2
1491.5
1199.7
921.4
652.2
427.3
390.1
Age structures for the Canadian and Mexican populations
for the year 2000 (from the United States Bureau of the Census)http://www.mcgrawhill.ca/links/biology12
If you would like to build and compare age pyramids for other
countries or regions, go to the web site above, and click on
Web Links.WEB LINK
512 MHR • Unit 5 Population Dynamics
Six thousand years ago, Mesopotamian farmers
dug ditches from the rivers that surrounded the
plain on which they grew their crops. These
ditches not only controlled seasonal floods, but
also provided water when it was desperately
needed during dry periods. These ancient irrigation
ditches were very successful for a long time. High
crop yields supported a large population in which
trade and social roles became highly diversified, as
illustrated in Figure 15.7 on page 513. Knowledge
increased and systems of government developed to
organize the large number of people in new cities
and states.Over time, however, the soil became less and
less fertile. Surplus irrigation water was not
removed from the land, and it left behind salts and
other toxins as it evaporated. Farmers switched
from wheat to the more salt-tolerant barley, but
eventually it also became difficult to grow. The
previously forested hills above the flood plain
became denuded as larger numbers of people
sought fuel, building materials, and land on which
to grow crops and graze animals. Some of the
ancient cities of Mesopotamia seemed to fade away
from lack of food, others apparently succumbed to
massive floods or mudslides caused by soil erosion
on the cleared hillsides.