Population Pyramids

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Population Pyramids

• We are working through pages
• 175 to 178

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An Introduction to Population Pyramids

• The composition of any population, that is, the
  ages and sex of the members of that population,
  is of particular interest to demographers.
• Typically demographers categorize any population
  into its male and female components by age
  divisions called cohorts. The most common cohorts
  are divided into 5 year intervals.
• This information can be presented using an
  age-sex structure called a population pyramid, as
  the information pertaining to countries resemble
  a triangular or pyramidal shape.
• In a population pyramid, bars indicating the male
  portion of the population extend to the left of a
  vertical axis, while bars indicating the female
  portion extend to the right.
• The bars are stacked on top of each other,
  starting with the bars for the youngest cohort at
  the bottom.

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1996 Census of Population
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• In modern times a population pyramid tends to be
  classified as either expansive or stationary.
• Expansive Age-sex Structure A population pyramid
  with a wide base and narrower top. This indicates
  a high birth rate and an expanding population.
• Population pyramids of LDCs (Less Developed
  Countries) typically have a wide base and a
  narrow top. This represents a high birth rate and
  high death rate.
• Stationary Age-sex Structure A population
  pyramid that indicates no or very little
  population growth. Stationary age-sex structures
  are characteristic of countries where both the
  death rate and birth rate are very low. The
  pyramid is characterized by relatively straight
  sides.
• Population pyramids of MDCs (More Developed
  Countries) typically have a roughly equal
  distribution of population throughout the age
  groups. The top obviously gets narrower as a
  result of deaths.

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Different Ages Different Roles

• At each stage of our lives, we play different
  roles. Demographers identify three important
  stages
• Children (up to age 15)
• Working adults (ages 16 to 64)
• Other adults (65 and over)
• The assumption is that children and older adults
  are not working and must be supported by the
  working population.
• The proportion of the population that must be
  supported is called the dependency ratio. We can
  calculate the dependency ratio by adding together
  the percentage of those under fifteen and those
  over sixty-four, and then dividing this sum by
  the percentage of those in the potential labour
  force (ages 15 to 64).
• For example, (see page 175 in the text) using the
  population pyramid of Canada in 1961, the
  dependency ratio for each member of the potential
  work force, plus himself or herself, supports
  0.73 or you could say that there are 73
  dependants for every 100 people in the potential
  labour force.
• Percent under 15 percent over 64 33.8 8.4
• 
  Percent 15-64
  57.8

0.73
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• A high dependency load, of either children or
  older people, tends to put a great deal of
  pressure on the society to provide education,
  housing, health care, old-age homes, and other
  needs.
• Canada today has a dependency load of 33 (21
  children and 12 older people), while a country
  like Niger in north Africa has a dependency load
  of 52 (49 children and only 3 older people).
• You can imagine the difficulty that a country
  like Niger would have in trying to support the
  more than half of its population that is
  dependent.

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Turn to page 177

• Refer to Q. 27 (a) Begin this question by
  constructing a population pyramid for Japan.
  Refer to Figure 7.28 for your data information.
  Use landscape form. Label the population pyramid
  at the top of the page Japan (1997).
• Next, Count over 28 squares and draw a line from
  the top of the graph to the bottom. Draw a line
  from the bottom of line 32 upwards. Between these
  two established lines are your age groups. Every
  two rows equals an age group, starting at 0-4 and
  finishing the pyramid at 80).
• On the left-side of the pyramid is your male
  percentages, and on the right-side of the
  population is your female percentages. On either
  side of the age group bar in the middle, each
  line going over is .25 percent. Start at zero
  (age group lines).
• Materials (1) Use the graph paper that has been
  provided. (2) You will require two colour
  pencils. Use one colour to shade in the bars for
  male percentages on your pyramid. Choose an
  additional colour to shade in the bars
  representing the female percentages.

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Age-sex Distribution for Japan (1997)
Male Age Group Female
2.4 0-4 2.3
2.5 5-9 2.4
2,9 10-14 2.8
3.3 15-19 3.1
3.9 20-24 3.7
3.9 25-29 3.7
3.3 30-34 3.2
3.1 35-39 3.1
3.3 40-44 3.3
4.3 45-49 4.3
3.4 50-54 3.5
3.2 55-59 3.3
2.9 60-64 3.1
2.5 65-69 2.8
1.8 70-74 2.3
1.0 75-79 1.7
1.1 80 2.2
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Turn to page 178

• Once you constructed the pyramid for Japan, using
  the data in Figure 7.28 on page 178, construct a
  population pyramid for Malawi. Follow the steps
  used in the instructions for constructing the
  population pyramid fro Japan. In counting over
  from the age groups, count each block as.5
  instead of .25.
• Once completed, answer Q. 27 (PARTS B, C, D, and
  E) for the population pyramids for Japan and
  Malawi.

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Age-sex Distribution for Malawi (1997)
Male Age Group Female
8.5 0-4 8.4
7.6 5-9 7.6
6.9 10-14 6.8
5.9 15-19 5.8
4.9 20-24 4.7
3.9 25-29 3.7
2.8 30-34 2.8
2.1 35-39 2.2
1.6 40-44 1.9
1.4 45-49 1.7
1.1 50-54 1.4
0.9 55-59 1.2
0.7 60-64 0.9
0.5 65-69 0.7
0.3 70-74 0.5
0.2 75-79 0.2
0.1 80 0.1
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Demographic Transition Models
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The Demographic Transition Model

• The Demographic Transition Model attempts to show
  how population changes as a country develops. The
  model is divided into four stages.
• Stage 1Birth rate and death rate are high - low
  natural increase - low total population
• Stage 2 Birth rate is high - death rate is
  falling - high natural increase (population
  growth)
• Stage 3Falling birth rate - low death rate -
  high natural increase (population growth)
• Stage 4Birth rate and death rate is low - low
  natural increase - high total population

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Population Changes in LDCs

• The populations of less developed countries
  (LDCs) are growing very rapidly. Most are at
  stage 2 and 3 of the Demographic Transition
  Model. They have declining deaths rates and high
  birth rates. Therefore, natural increase is high.
  
• Death rates are declining because of improvements
  in sanitation and healthcare.
• Birth rates are high for a number of reasons
• Lack of family planning education or
  contraceptives
• In rural areas children are needed as labour on
  farms. In urban areas they are needed to work in
  the informal sector to earn money for their
  families.
• Women have a large number of children as there is
  a high level of infant mortality
• Culture/religion mean it is unacceptable to use
  contraceptives

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Population Changes in MDCs

• In most MDCs population growth is stable. MDCs
  have low birth and death rates. In some countries
  (i.e. Germany) the birth rate is actually lower
  than the death rate. This means there is a
  decrease in population versus a natural increase
  (Germany is -0.1).
• The major problem for many MDCs is an ageing
  population.
• Life expectancy in MDCs is increasing as people
  are now living longer due to improvements in
  health care, diet and lifestyle.
• Therefore, there will be a a greater number of
  elderly dependents. In the UK this is likely to
  lead to increased taxes to pay for health care
  and pensions.

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Sources

• http//www.census.gov/ipc/www/idbpyr.html
• http//www.geography.learnontheinternet.co.uk/