I N
Concept:
The age and gender distribution of a
national population affects its
growth rate. By creating age-sex distribution charts (often called “population pyramids”) you can tell much
about a nation’s demographic history and project its future.
Objectives:
Students will be able to:
• Calculate percentages using raw
numbers for each age/gender group
in a given population.
• Construct a population age/gender distribution graph for four different years in U.S. history and one
using future projections.
• Make correlations between the
shapes of the graphs and the characteristics that may have affected
U.S. population patterns at different
time periods.
Subjects:
Math, biology, social studies,
environmental science
Skills:
Graphing, analyzing and interpreting data
Method:
Students construct and interpret
population pyramids and discuss
differences in population characteristics at different points in U.S. history and make projections for the
future.
T H E
U S A
Mysteries of the U.S. Pyramids
Introduction:
To help them make population projections for different countries, demographers
look at the profile of the countries’ residents. What are the ages of the people? How
many are men? How many are women? This information is essential in planning the
size and spending for government programs that serve the population. Demographers use these figures to construct “population pyramids” like the ones students
will create in this activity. These graphs depict the configuration of a country’s population in cohorts (5-year age groups) as impacted by 70 to 80 years of economic,
political and natural events. These graphs can also help predict future population
trends. In this activity, students will construct “population pyramids” for four different points in U.S. history and a pyramid for a projected population in the future.
Through discussion questions, they will analyze and interpret the data and charts
they have created.
Materials:
Student Worksheets (one per student)
Graph paper
Colored pencils or markers
Calculator
Procedure:
1. Display the sample world population pyramid and explain that this is a kind of graph
used by demographers to study the distribution of people across age categories.
2. Assign each student or group of students one of the five years (1880, 1920, 1960,
2000 or 2050) and distribute graph paper and a copy of the student worksheet for
that year.
3. The figures on the worksheet represent the population (in thousands) of each age
group within each gender for each particular year. In order to construct the U.S.
pyramid for that year, demographers must first calculate the percentage of the
population in each gender in each age group.
Example: According to the worksheet, the United States’ total population in 1880
was 50,155,000. The population of males ages 0-4 was 3,508,000.
Population
3,508,000 = 0.07 or 7%
50,155,000
Quality of Life
You may have students complete these calculations for each cohort (age group),
or, in the interest of time, provide them with the percentages.
© Population Connection, 2014
Mysteries of the U.S. Pyramids
4. Using the graph paper provided, students can construct a population pyramid as in the example. A line
drawn down the middle of the graph separates the male and female populations. The percentages of the population will be plotted along the X-axis — females to the right, males to the left of the center line. The age
groups will be running up the Y-axis with the youngest at the bottom, oldest at the top. (See “World Population Pyramid” sample.)
5. Have students graph the percentage data for their assigned year.
6. Have students hold up their finished graphs for all to see while going through the follow-up questions in class.
World Population Pyramid
AGE
MALE
FEMALE
75+
70-74
65-69
60-64
55-59
50-54
45-49
40-44
35-39
30-34
25-29
20-24
15-19
10-14
5-9
0-4
9
8
7
6
5
4
3
2
1
0
1
2
3
4
5
6
7
8
9
Percentage of Population
Source:
U.S. Census Bureau; www.census.gov, 2012
© Population Connection, 2014
Mysteries of the U.S. Pyramids, page 2
Sample Pyramids
AGE
1880
MALE
FEMALE
AGE
75+
70-74
65-69
60-64
55-59
50-54
45-49
40-44
35-39
30-34
25-29
20-24
15-19
10-14
5-9
0-4
9
AGE
1920
MALE
FEMALE
75+
70-74
65-69
60-64
55-59
50-54
45-49
40-44
35-39
30-34
25-29
20-24
15-19
10-14
5-9
0-4
8
7
6
MALE
5
4
3
2 1 0 1 2 3 4 5
Percentage of Population
1960
6
7 8 9
9 8
FEMALE
AGE
75+
70-74
65-69
60-64
55-59
50-54
45-49
40-44
35-39
30-34
25-29
20-24
15-19
10-14
5-9
0-4
7 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 9
Percentage of Population
2000
MALE
FEMALE
75+
70-74
65-69
60-64
55-59
50-54
45-49
40-44
35-39
30-34
25-29
20-24
15-19
10-14
5-9
0-4
9 8
7 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 9
Percentage of Population
AGE
9
8
7
6
5
4
3
2
1
0
1
2
3
4
5
6
7
8
9
Percentage of Population
2050
MALE
FEMALE
75+
70-74
65-69
60-64
55-59
50-54
45-49
40-44
35-39
30-34
25-29
20-24
15-19
10-14
5-9
0-4
9
8
7
6
5
4
3
2
1
0
1
2
3
4
5
6
7
8
9
Percentage of Population
© Population Connection, 2014
Mysteries of the U.S. Pyramids, page 3
Discussion Questions:
1. Which of the graphs look most like pyramids? Does that indicate slow or rapid population growth during
those time periods? Why? Which graph looks most like the current world population graph shown in the
sample?
The graph for 1880 looks most like a pyramid, followed by the graph for 1920. The pyramid shape indicates
rapid growth because most of the population is in the younger cohorts. In 1880, over 38 percent of the population was under the age of 15, still yet to approach their reproductive years. The U.S. graph for 1920 looks
similar to the current world population graph, which shows most of the population in the younger cohorts,
even as the growth rates appear to be slowing.
2. In 1880, there are the same percentages of males and females at age 20-24. However, for the next two cohorts (25-29 and 30-34), the percentage of females is significantly lower than that of males. Why might that
be the case?
Until the mid-1930’s maternal mortality rates (women dying as a result of pregnancy or childbirth) were
quite high with rates approaching one percent (900 deaths/100,000 live births) in the late 19th century. Most
of these maternal deaths were due to bacterial infections. With the advent of sulfonamides and penicillin, as
well as safer obstetrical procedures and antiseptic conditions in delivery rooms, maternal mortality rates fell
dramatically. Today, maternal mortality stands at 21 deaths/100,000 live births in the U.S.1
3. Looking at the data chart, what do you observe about the gender balance for the different age cohorts in
2000? What factors do you think might contribute to this?
There are more males than females in each cohort from birth to age 34. Then, there are more females in
every cohort from age 35 on, especially among the population over 70 years of age. Statistically, there are
more boys born each year than girls (105 boys for every 100 girls). However, life expectancy for women is
higher than for men, due to a number of genetic and social factors. In the U.S. the current life expectancy is
76 for men and 81 for women.2 In general, men are more predisposed to certain health risks than women,
although this gap is narrowing.
4. Looking at your graph for 1960, which are the two smallest cohorts in the U.S. population? Why might that
be the case? Which are the three largest cohorts that year? Why might that be the case?
The smallest cohorts in 1960 were men and women between the ages of 25-29 and 20-24 respectively. These
were children born during the Great Depression years of 1931-40. Following the stock market crash of 1929
was a decade of historically high rates of unemployment and poverty in the United States. At times of economic depression, couples tend to have fewer children. By contrast, the three largest cohorts in 1960 were
the youngest members of society (0-4; 5-9; and 10-14 year olds). These children were born during the economic prosperity of the post-World War II years of 1946-1960. Members of this “Baby Boom” generation
still comprise the largest cohorts of our present population.
5. Current news stories about U.S. demographics often refer to the “graying of America.” What do you think
this means and why might it be happening?
The “Baby Boom” generation (born 1946-1964) is now entering retirement and will create the largest group
of senior citizens in American history. At the same time, life expectancy has been increasing over the years
due to medical advances and healthier lifestyles. From 1950 to 2000 the percentage of the population age
75 and older rose from 3 to 6 percent. By 2050, it is projected that 21 percent (1 in 5) Americans will be 65
or older.3
© Population Connection, 2014
Mysteries of the U.S. Pyramids, page 4
6. Which of the pyramids shows the slowest rate of population growth? How can you tell?
The pyramid for 2050 shows the slowest rate of growth. The graph is closer to a rectangle than a pyramid,
showing more uniform population size across the age groups.
7. What do you think are some of the variables that demographers considered in coming up with this projection? What are some factors that could change this projection?
In creating the projection for 2050, demographers would have considered birth and death rates, life expectancy and total fertility rates (number of children a woman has on average). Fertility rates can be affected by economic conditions, as we saw during the Great Depression and Baby Boom and by access to
reproductive health services. Life expectancy rates can vary depending on prevailing healthcare trends, advances in medical technology, and outbreaks of pandemics. The current projections, as evidenced by the
chart for 2050, seems to suggest a balanced population with replacement-level fertility creating equal-size
cohorts and a high life expectancy, especially for females.
Sources:
1
CIA World Factbook, 2012. www.ciaworldfactbook.gov
2,
2013 World Population Data Sheet, Population Reference Bureau.
3
“Percent Distribution of the Projected Population by Selected Age Groups and Sex for the United States: 2015-206,” (NP2012-T3), U.S.
Census Bureau.
© Population Connection, 2014
Mysteries of the U.S. Pyramids, page 5
© Population Connection, 2014
Mysteries of the U.S. Pyramids, page 6
3,508
3,275
2,907
2,476
2,555
2,110
1,744
1,527
1,244
1,079
967
675
585
379
250
238
25,519
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+
Total
Total
M
Age
Group
24,636
264
245
346
519
596
873
1,011
1,225
1,473
1,625
1,971
2,533
2,535
2,808
3,205
3,407
F
50,155
50.9
0.5
0.5
0.8
1.2
1.3
1.9
2.2
2.5
3.0
3.5
4.2
5.1
4.9
5.8
6.5
7.0
%
1880
49.1
0.5
0.5
0.7
1.0
1.2
1.7
2.0
2.4
2.9
3.2
3.9
5.1
5.1
5.6
6.4
6.8
%
54,291
690
711
1,084
1,601
1,901
2,582
3,052
3,406
4,129
4,133
4,644
4,531
4,760
5,355
5,823
5,889
M
52,170
759
691
994
1,422
1,695
2,230
2,641
3,133
3,714
3,962
4,677
4,708
4,822
5,280
5,700
5,742
F
106,461
51.0
0.6
0.7
1.0
1.5
1.8
2.4
2.9
3.2
3.9
3.9
4.4
4.3
4.5
5.0
5.5
5.5
%
1920
Population in Thousands
49.0
0.7
0.6
0.9
1.3
1.6
2.1
2.5
2.9
3.5
3.7
4.4
4.4
4.5
5.0
5.4
5.4
%
89,320
2,409
2,197
2,936
3,414
4,145
4,763
5,379
5,732
6,140
5,904
5,423
5,569
6,803
8,602
9,565
10,339
M
91,353
3,213
2,577
3,344
3,741
4,326
4,901
5,535
5,946
6,403
6,079
5,512
5,566
6,640
8,323
9,245
10,002
F
180,673
49.3
1.3
1.2
1.6
1.9
2.3
2.6
3.0
3.2
3.4
3.3
3.0
3.1
3.8
4.8
5.3
5.7
%
1960
Mysteries Of The U.S. Pyramids - Answers to Student Worksheet #1
50.7
1.8
1.4
1.9
2.1
2.4
2.7
3.1
3.3
3.5
3.4
3.1
3.1
3.7
4.6
5.1
5.5
%
Mysteries Of The U.S. Pyramids
Answers to Student Worksheet #2
Population in Thousands
2000
2050
19
Age
Group
M
%
F
%
M
%
F
%
M
%
0-4
9,831
3.5
9,387
3.3
12,329
3.1
11,786
2.9
10,339
5.7
5-9
10,489
3.7
9,994
3.5
12,266
3.1
11,717
2.9
9,565
5.3
10-14
10,561
3.7
10,048
3.6
12,119
3.0
11,563
2.9
8,602
4.8
15-19
10,413
3.7
9,837
3.5
12,120
3.0
11,552
2.9
6,803
3.8
20-24
9,822
3.5
9,363
3.3
12,590
3.1
11,873
3.0
5,569
3.1
25-29
9,785
3.5
9,531
3.4
13,115
3.3
12,377
3.1
5,423
3.0
30-34
10,373
3.7
10,214
3.6
13,322
3.3
12,627
3.2
5,904
3.3
35-39
11,305
4.0
11,343
4.0
13,069
3.3
12,444
3.1
6,140
3.4
40-44
11,180
4.0
11,355
4.0
12,586
3.1
12,069
3.0
5,732
3.2
45-49
9,959
3.5
10,271
3.6
12,337
3.1
11,925
3.0
5,379
3.0
50-54
8,707
3.1
9,084
3.2
12,095
3.0
11,772
2.9
4,763
2.6
55-59
6,553
2.3
7,006
2.5
12,145
3.0
11,949
3.0
4,145
2.3
60-64
5,166
1.8
5,699
2.0
11,081
2.7
11,267
2.8
3,414
1.9
65-69
4,403
1.6
5,131
1.8
9,767
2.4
10,378
2.6
2,936
1.6
70-74
3,904
1.4
4,946
1.8
8,253
2.1
9,157
2.3
2,197
1.2
75+
6,145
2.2
10,533
3.7
19,576
4.9
26,608
6.7
2,409
1.3
Total
138,596
49.1
143,742
50.9
198,770
49.5
201,037
50.3
Total
© Population Connection, 2014
282,338
89,320 49.3
399,807
Mysteries of the U.S. Pyramids, page 7
180
,673
© Population Connection, 2014
379
250
238
25,519
65-69
70-74
75+
Total
91,353 50.7
585
1.8
60-64
3,213
675
1.4
55-59
2,577
967
1.9
50-54
3,344
1,079
2.1
45-49
3,741
1,244
2.4
40-44
4,326
1,527
2.7
35-39
4,901
1,744
3.1
30-34
5,535
2,110
3.3
25-29
5,946
2,555
3.5
20-24
6,403
2,476
3.4
15-19
6,079
2,907
3.1
10-14
5,512
3,275
3.1
5-9
5,566
3,508
3.7
0-4
6,640
24,636
264
245
346
519
596
873
1,011
1,225
1,473
1,625
1,971
2,533
2,535
2,808
3,205
3,407
54,291
690
711
1,084
1,601
1,901
2,409
89,320
52,170
2,197
2,936
3,414
4,145
4,763
5,379
5,732
6,140
5,904
5,423
5,569
91,353
3,213
2,577
3,344
3,741
4,326
4,901
5,535
5,946
6,403
6,079
5,512
5,566
6,640
8,323
8,602
6,803
9,245
10,002
F
9,565
10,339
759
691
994
1,422
1,695
2,230
2,641
3,052
2,582
3,133
3,714
3,962
4,677
4,708
4,822
5,280
5,700
5,742
F
3,406
4,129
4,133
4,644
4,531
4,760
5,355
5,823
5,889
%
1960
%
4.6
M
8,323
M
%
5.1
%
9,245
%
F
5.5
M
10,002
Age
Group
%
1920
60
1880
F
Population in Thousands
%
Name ________________________
Date __________________________
Student Worksheet, Page 1
Mysteries Of The U.S. Pyramids
Mysteries of the U.S. Pyramids, page 8
Name ________________________
Date __________________________
Student Worksheet, Page 2
Mysteries Of The U.S. Pyramids
Population in Thousands
2000
2050
Age
Group
M
0-4
9,831
9,387
12,329
5-9
10,489
9,994
10-14
10,561
15-19
%
F
%
M
%
F
%
M
%
11,786
10,339
5.7
12,266
11,717
9,565
5.3
10,048
12,119
11,563
8,602
4.8
10,413
9,837
12,120
11,552
6,803
3.8
20-24
9,822
9,363
12,590
11,873
5,569
3.1
25-29
9,785
9,531
13,115
12,377
5,423
3.0
30-34
10,373
10,214
13,322
12,627
5,904
3.3
35-39
11,305
11,343
13,069
12,444
6,140
3.4
40-44
11,180
11,355
12,586
12,069
5,732
3.2
45-49
9,959
10,271
12,337
11,925
5,379
3.0
50-54
8,707
9,084
12,095
11,772
4,763
2.6
55-59
6,553
7,006
12,145
11,949
4,145
2.3
60-64
5,166
5,699
11,081
11,267
3,414
1.9
65-69
4,403
5,131
9,767
10,378
2,936
1.6
70-74
3,904
4,946
8,253
9,157
2,197
1.2
75+
6,145
10,533
19,576
26,608
2,409
1.3
Total
138,596
143,742
198,770
201,037
© Population Connection, 2014
89,320 49.3
Mysteries of the U.S. Pyramids, page 9
Name ________________________
Date __________________________
Mysteries of the U.S. Pyramids Graph Paper
Date __________________
AGE
75+
F
70-74
65-69
60-64
55-59
50-54
45-49
40-44
35-39
30-34
25-29
MALE
FEMALE
AGE
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40-44
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20-24
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15-19
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Percentage of Population
© Population Connection, 2014
Mysteries of the U.S. Pyramids, Graph Paper