Activity 3: Constructing and Interpreting Age-Sex Graphs

Introduction

What Is an Age-Sex Graph?

An age-sex graph, commonly referred to as a population pyramid even though the graph for some countries is not actually a pyramid shape, displays a population's age and sex composition. Horizontal bars represent the numbers or proportions of males and females in each age group, or cohort. The sum of all the age-sex cohorts in the population pyramid equals 100 percent of the population. Cohorts may vary from single years to groups of years.


Example Age-Sex Graphs with Five-Year Cohort


The left side of the pyramid represents the male population and the right side, the female population. The bars at the bottom of the pyramid represent the percent of the population that is male, 0-4 years old (left) and the percent of the population that is female, 0-4 years old (right). Each bar above the base represents the next five-year cohort, male and female, in the population. As cohorts age, they inevitably lose members because of death and they may gain or lose members because of migration. After age 45 the loss of population accelerates, causing the narrowing peak of all population pyramids.

Population pyramids reveal a great deal about a population at a glance. Populations of countries can differ markedly as a result of past and current patterns of fertility, mortality, and migration.


Part One: How Do You Construct an Age-Sex Graph?

Materials Needed

  • Population Handbook, 5th edition (PDF: 380KB)
  • Population: A Lively Introduction, 3rd edition (PDF: 260KB)
  • Handout 1. "Age-Sex Graph" (PDF: 17KB)
  • Handout 2. "Age-Sex Data Table" (PDF: 15KB)
  • Colored pencils
  • Calculator

Instructions

In order to understand how to interpret population pyramids, read the following selections from PRB publications:

  • Population Handbook, 5th edition (PDF: 380KB)
  • Population: A Lively Introduction, 3rd edition (PDF: 260KB) , pp. 23-28.
  1. Provide each student with a copy of the "Age-Sex Graph" handout, colored pencils, and the age-sex data table. Also transfer a copy of the graph to a transparency for use as a demonstration.
  2. Explain that the raw population numbers need to be converted to percents before beginning to construct a pyramid. This can be done using a calculator or using a spreadsheet, such as MS Excel. [Divide the population of each cohort by the total population of the country to determine what percent of the total population is in each cohort.]
  3. Using the graph transparency, demonstrate how to transfer the data (%) for the first pyramid by drawing the bar for the first male cohort (0-4 years) to the left, and for the first female cohort (0-4 years) to the right. Have students proceed on their own, completing pyramids for both country A and country B.
  4. When students have completed both pyramids, lead a discussion of the similarities and differences in the shapes of the two pyramids. Based on the readings noted above, what inferences can be drawn about social and economic circumstances in each country? What might be some reasons for the differences in the two pyramids?

Part Two: How Do You Interpret Age-Sex Graphs?

Materials Needed

Instructions

In this activity students will analyze demographic data for selected countries of the world. They will also construct population pyramids and speculate on differences in the quality of life in these countries.

  1. Assign students (or pairs of students, depending on class size) one country from the list below. Direct students to locate the most current age-sex data for their assigned country.
    Column A
    Column B
    Argentina Bangladesh
    France Brazil
    Germany Egypt
    Israel Ethiopia
    Japan Indonesia
    New Zealand Thailand
    Russia Turkey
    United Kingdom Vietnam

    Open the U.S. Census Bureau "International Database," available at: www.census.gov/ipc/www/idbnew.html

    Choose "Summary Demographic Data."

    Select the assigned country from the country list. Then "Submit Query."

    Print or copy the data for the country. [Note: Disregard pyramids that appear on the Census IDB site. These are based on absolute numbers and are not appropriate for use in this activity.]

    Use the Census Bureau website to complete the chart below for the assigned country.

    Country: ____________________________________

     

    Demographic Variable
    Value
    Birth Rate (per 1,000)  
    Death Rate (per 1,000)  
    Natural Increase (%)  
    Infant Mortality Rate (per 1,000 live births)  
    Total Fertility Rate  
    Population <15 yrs. (%)/>65 yrs. (%)  
    Life Expectancy at Birth (male/female)  
    Urban Population (%)  
    GNP/capita (U.S.$)  
    1. Construct a pyramid for the assigned country either manually using a copy of the graph template, or by following the steps for pyramid construction using MS Excel (see  instructions provided under Materials Needed).
    2. Compare the demographic variables and the pyramid for the country. How does the pyramid reflect the variables? [for example, how is Birth Rate reflected in the base of the pyramid?]
    3. Characterize the level of development in the country—high, medium, low? Use two specific examples from the table and pyramid to support the decision about level of development.
    4. Have students with pyramids in the "a" group compare their pyramid with a pyramid from the "b" group. Have them also compare the demographic variables for both countries. What generalizations can be made concerning demographic indicators and level of development? [for example, if the birth rate is high, then the level of development is...] Encourage students to form at least three generalizations that are supported by the pyramids and data charts.
    5. Lead a class discussion on the use of population data and graphs as tools for analysis of population structure and composition. Describe the age/gender patterns you observe. Discuss the implications of the patterns. Think about the kinds of problems that could occur because of the differences in lifestyle and community priorities for different age groups in each location. Identify some investments (stores, entertainment, etc.) that might do well or some social programs (child care, education, medicine, etc.) that might be required in places with these populations.