Presentation3.pptx

Population Pyramids
1) A population pyramid graphically illustrates the
age and gender distribution of a given
population.
2) The shape of the pyramid conveys details about
life expectancy, birth, fertility,
and mortality rates.

Population Pyramids
1) Additional data that can be extrapolated from a
population pyramid include the effects of historical
events, economic development, and future
demographic trends.
2) This information helps direct plans for the
subsequent social and economic needs of a given
population.

Characteristics of Population Pyramid
i. Numbers are really good for describing things in
a very accurate way. Numbers tells us what % of
the population is a certain age and gender.
ii. A population pyramid is a way to visualize two
variables: age and sex and shows sex/age
structure of a Country.

i. A population pyramid is a visual representation
of any population split up by age groups. This can
be about a city, a country, or even the world.
ii. The pyramid consists of gender and age
categories that usually go by decade, so 0 to 10,
11 to 20, 21 to 30, and so on.

i. The graphic starts from youngest at the bottom
to oldest at the top.
ii. It is called a population pyramid because when
a population is growing (there are more babies
being born than there are people dying), the
graphic forms the shape of a triangle.

i. A population pyramid can be used to compare
differences between male and
female populations of an area.
ii. They also show the number of dependents (children
and, sometimes, elderly people) and general structure
of the population at any given moment.

i. There are three main trends in populations that
affect the shape of a population pyramid.
ii. The first is when there are both high fertility and
high mortality rates among younger members.

i. This type of population, known as “expansive,”
creates a sharp triangle shape in the graph.
ii. Expansive pyramids mean that
the population does not increase much in total
number and has many young people.

i. The second trend, known as “constrictive,” is when
there is a lower mortality rate with the fertility rate
remaining constant.
ii. These population pyramids are wider in the middle of
the graph as the population has high numbers of
middle aged and elderly people, but fewer young
people.

i. The third trend is “stationary” which is a population with
low mortality and low fertility rates.
ii. These graphs have a square or “pillar” shape rather than a
pyramid one.
iii. These population pyramids represent a stable population that
will not change significantly barring any sudden changes
to fertility or mortality rates.

Use of Population Pyramids
i. Population pyramids are useful for studying the
future of a region as well as examining historical
and current population trends.
ii. Population pyramids can also help direct
government and private industry distribution of
services for regions based on population needs.

Use of Population Pyramids
i. If part of the population has been affected by
sudden changes, such as casualties from armed
conflict, high female mortality in childbirth, or the
migration of young workers out of poorer regions,
the graph will offer a way to visualize how the
future population will be affected.

i. A population pyramid is a graph which shows the age-sex
distribution of a country’s population at a given time.
ii. This diagram shows the variation of both, the male and female
populations with age, which is not possible with conventional
bar graphs, and results in a pyramidal structure.
iii. The country’s population is shown on the X-axis, while the age
is displayed on the Y-axis in 5-year groups, called ‘cohorts’.
Population Pyramids

Cohort
A cohort: A specific portion of the population that is
combined together in an age-group for the purposes of
simplifying a population pyramid.
i. A group of people of a certain age
ii. Used to determine trends and see similarities and
differences.
iii. 5 years groups are most common

Overview - Definitions
A. Population pyramid:
i. Age-gender pyramid
ii. A graphical illustration showing the age-sex distribution of a
population
B. Birth rate (or crude birth rate): number of live births per
1,000 populations in a given year
C. Fertility rate: births per 1,000 women of childbearing age
(aged 15–44) in a given year

i. Death or mortality rate (or crude death
rate): number of deaths per 1,000 populations in a
given year
ii.Life expectancy: average number of additional
years a person could expect to live if
current mortality trends were to continue for the
rest of that person’s life.

A. Structure
I. Uses 2 juxtaposed histograms (generally 1 for each gender),
turned sideways:
1) Vertical (y-axis):
i. Age of the population
ii. Age groups displayed in the central axis
iii. Males: left of the vertical axis
iv. Females: right of the vertical axis

1. Horizontal axis (x-axis): percentage or size of the
population.
A. Illustrates a series of stacked bars, with each bar
representing the population and the age group.
i. Youngest age group: represented by the bottom bar
ii. Oldest age group: uppermost bar

A. Long-term trends of fertility and mortality rates:
a. Fertility rate:
i. Important influence on the shape of the pyramid
ii. Represented by the width or base of the pyramid
iii. More children = broader base
b. Death rate: slope of the pyramid
c. Life expectancy: height of the pyramid
Uses of the Population Pyramid
Population trends

A. Short-term trends and significant events:
i. Kinks or indents in the pyramid: indicate decline in birth rates
or increase in death rates (e.g., wars, famine, disease)
ii. Bulges in the pyramid: indicate increase in birth rates (e.g.,
baby booms)
B. Information about sex ratio of a population and effects of migration
C. Data on future growth of the population:
i. Median age of the population: lower median age, higher
population growth
Interpretation of Population Pyramid
Population trends

Interpretation of the Population Pyramid
Population trends

A. Future needs
i. Forecasts social and economic needs for national planning
based on the distribution of the population's age groups:
i. Working-age population (15–64 years)
B. Dependents:
i. Children and young adolescents (under 15 years old)
ii. Elderly population (65 years and older)
Interpretation of the Population Pyramid
Population trends

Dependency Load
i. The number of people who are too old or too young to support
themselves.
ii. They are dependent on the rest of the society for survival.
iii. Generally it includes people who are under 15 years or over 65
years.
iv. The higher this number is, the more taxes have to be paid for
schools,hospitals,daycare,Social cash transfers for the aged etc.

Dependency Ratio
i. Age – population ratio of those typically not in the
labour force (the dependent part) and those typically in
the labour force (the productive part).
ii. This ratio gives an indication of the level of economic
development in the country as the higher the
percentage of people of working age a country has the
better off economically they should be.

A. Dependency ratio:
i. Ratio between dependents and the working group
ii. Higher ratio: more dependents
B. Youth dependency ratio:
i. Ratio between youth < 15 years of age and the working-age group
ii. High youth dependency ratio: plan for housing, education, schools
C. Old-age dependency ratio:
i. Ratio between those > 65 years of age and the working-age group
ii. High old-age dependency ratio: plan for health care, pension, nursing
homes
Dependency Ratio

1. Young dependants (YD): Anyone younger than 15
years.
2. Old dependants (OD): Anyone 65 years and older.
3. Dependency ratio = Number of people 0-14(YD)
+Number of people 65+ years/ Number of people aged
15 -65 working x 100
Dependency Ratio

Population Pyramid –
Descriptive Epidemiology

Stationary population pyramids
i. Stationary population pyramids are characterized by their
more rectangular shape which indicate that the population is
not growing.
ii. The percentages of each age group is relatively equal
throughout before tapering off toward more elderly age groups.
iii. These population pyramids tend to reflect populations where
birth rates are relatively low, but the overall quality of life is
high.

Stationary pyramid
A. Stationary pyramid
i. Overall shape is a rectangle, tapering at the top.
ii. Describes a population with:
a. Low fertility rate
b. Low mortality rate
c. High life expectancy
d. Almost equal percentages in the age groups
iii. Indicates slow growth of the population
iv. Seen in developed countries

Stationary - Slow Growth Population
i. All age groups similar
ii. Birth and death rates low
iii. Life expectancy high
iv. Less and less babies
v. No growth
vi. Birth rate = death rate

Stationary population pyramid (United States) in 2017, showing even bars
indicating that most age groups are almost equal in size.

Expansive Population Pyramid
i. Expansive population pyramids characterized by
an obvious triangular shape, with a broad base
that tapers toward a narrow top.
ii. These population pyramids depict and describe
populations which are young, but growing.

i. This is expressed by the much larger percent of the
population being comprised of younger age groups.
ii. Expansive population pyramids typically depict
developing nations, or those with high fertility
rates, but low life expectancy or high mortality
rates.

A. Expansive pyramid
i. Overall shape is an upright pyramid, with a broad
base.
a) High fertility rate
b) High mortality rate
c) Low life expectancy

A.Expansive pyramid
i. Each age group is smaller than the age group
before it.
ii. Indicates fast growth of the population, with
small share of older people
iii.Seen in developing countries

High birth and death rates in a population create a tapered
triangular population pyramid.

Expansive population pyramid (Nigeria): Note the wide base, which is
indicative of a high fertility rate.

i. Examples: Expansive populations : Such a
population pyramid is a characteristic of newly
developing countries such as Afghanistan,
Bangladesh, Kenya, and some countries of Latin
America.

Unstable population pyramid
i. High birth and death rates
ii. Low life expectancy
iii. Brings a countries medical system or political system into question.
iv. Lack of contraceptives
v. Lack of medical treatment
vi. Consider: Infant Mortality rate is high
vii. Wars
viii.Diseases

Constrictive Pyramid
i. A constrictive pyramid is the opposite of an expansive
pyramid, with a slight constriction in its younger age
groups.
ii. There is high life expectancy and good living
conditions in such a country, leading to a higher
number of older people.

i. Despite this, there is a lesser number of births taking
place, which is outnumbered by the number of deaths.
ii. This indicates a greying as well as decreasing population.
iii. There is a higher number of older people than the youth in
the country, which places a burden upon the working-age
population to support the large number of elderly
dependents.

i. The decrease in the number of births
indicates that people are choosing to have
lesser children, and may also be due to
increased emigration.

1. Examples: Developed European countries like Italy and
Germany, along with countries like Japan and Australia come
under this category.

i. Constrictive pyramid
i. Overall shape is an inverted pyramid, with a narrow
base.
i. Low fertility rate
ii. Low mortality rate
iii.High life expectancy

A. Constrictive pyramid
i. Narrowing at the bottom of the graph indicates that
the population is shrinking.
ii. Large share of the population is aging.
iii.Seen in wealthy, industrialized, developed countries
(high literacy, good access to birth control and
healthcare)

Constrictive population pyramid (Germany), showing a narrow
base, indicating a low birth rate.

Stable Pyramid
i. This type of population distribution shows a rectangular or
squarish shape, with almost the same number of people in all
age groups.
ii. There is a slight taper at the top, which is perfectly natural,
due to more deaths occurring among the elderly.
iii. Such countries have a high life expectancy, where more
people live to a ripe old age, due to better living conditions,
medical facilities, and geriatric care.

i. They also have a stable birth rate, as there is more awareness
and incentives to use birth control measures, along with the
empowerment of women.
ii. Such a pyramid shows a stable increase in the country’s
population with time.
iii. Examples: Highly-developed countries such as USA, Sweden,
and Netherlands, which have well-established economies, come
under this type.
Stable Pyramid

i. Slow growth rate
ii.Low birth and death rates
iv.Birth rate > Death rate
Stable Population Pyramid

i. Suggests a good medical system, availability of
contraceptives and medical treatment.
ii. Incomes increasing, standard of living
increasing ,children are becoming more of an
expense.
Stable Population Pyramid

i. No Country has reached this stage yet, therefore
this pyramid represents a prediction of future
trends.
ii. Low birth and death rates
iv.Death rate > Birth
Declining Population

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