Types of Pyramids

Categories of Population Pyramids
• Demographers may categorize population
pyramids into three groups based on shape.
• The three groups/shapes are:
– Expansive
– Stable/Stationary
– Contracting/Constrictive
Expansive Population Pyramids
• There are two types of expansive pyramids.
• Both types share common characteristics:
– Wide/Broad base
– Narrow top
• Thus, both will show larger numbers or
percentages of the population in the younger
age groups
Expansive Population Pyramids
Wide/Broad Base
• The wide base indicates a
high birth rate.
• The broader the base, the
higher the birth rate.
• A broad base also shows
that there are more young
people in the population.
Narrow Top
• The narrow top indicates a
high death rate and lower
life expectancy.
• The narrower and lower the
top, the higher the death
rate and the lower is the life
• A narrow top also shows
that there are fewer older
people in the population.
Expansive Population Pyramids 1
• The first type (sub-type) of expansive pyramid
may be called early expanding.
• Apart from the wide base, this pyramid is
characterised by concave sides caused by a rapid
fall in each upward age group.
• The concave sides are caused by high death rates
(which also results in a narrow top.)
• Populations in Stage 1 of the DTM will show such
a pyramid (few countries today fall into this
Population Pyramids- Early Expanding
Nigeria, 2005
Population Pyramids - Early Expanding
Scotland, 1861
Population Pyramids
- Early Expanding
Expansive Population Pyramids - 2
• The second type (sub-type) of expansive pyramid
may be called expanding.
• Apart from the wide base, it is characterised by
sloping sides.
• These are not concave, but are straighter and
may even be slightly convex around the youth
cohorts (0 – 14).
• The straighter sides and convex “youth bulge” are
both caused by falling death rates characteristic
of countries within Stage 2 of the DTM.
Expansive Population Pyramids - 2
• Here's an example of an expanding population
pyramid showing the population of Japan in
Notice how there are fewer males
than females as the population
This type of pyramid is quite
typical of many European nations,
the United States, Canada and
Australia after the Second World
War and, as stated above, is an
expanding population pyramid.
• Concave sides indicate a
high death rate.
• Straighter or convex sides
show a lower death rate.
• A very narrow top
that poor medical care
• A very wide base
which, in turn, is generally
indicative of a lower
standard of living where
there is limited access to
birth control.
• In this type of pyramid there are more children
than there are males and females in the
reproductive age groups meaning that the
population is more than replacing itself over
• These types of pyramids are usually found in
populations with very large fertility rates and
lower than average life expectancies.
• The age-sex distributions of many Third World
countries would probably display expansive
population pyramids.
Stable Population Pyramids
• The second type of pyramid is the stable or
stationary population pyramid.
The relatively wide and high
top to the pyramid indicates
that there is a low death rate
throughout life and access to
good medical care.
The base of the population pyramid is the
same width as the age range where
reproduction is most likely to take place.
This is generally indicative of a higher standard
of living where there is ready access to birth
Contracting Population Pyramids
• The third type of pyramid is a contracting or
constrictive population pyramid.
In these cases, the population is not
replacing itself; very low birth rates mean
that the population is likely to drop in the
These population distributions are usually
found in developed nations.
These pyramids have a
narrower base than the age
range where reproduction is
most likely to take place, and
don't really resemble a pyramid
at all.
Notice how the population of
the age groups between 0 and
14 years of age are much
narrower than those of the
between 15 and 44 years of
Contracting Population Pyramids
• As time progresses, this population will shrink
because Japan faces three issues:
– a very low birthrate,
– a long lifespan and
– a very low immigration rate.
Contracting Population Pyramids
• Here is the population pyramid showing the
projected population groups for Japan in the
year 2050:
Notice how there are many more senior
citizens (39.6 percent of the total
population) than there are young children
under the age of 15 (8.6 percent of the
Variations in Shapes
• Irregularities in the sides of a population
pyramid can be indicative of various issues.
• Bumps in the side can indicate sudden growth
in the population.
As shown in this example of
France, the circled bump
accompanying the birth of baby
boomers after World War II
travels up the pyramid with
time from the year 1970 to the
year 1985.
Asymmetrical Shapes
• Population pyramids show the distribution of
males versus females. Therefore, one can see
how the distribution of the two genders
changes with age.
In the 2050 chart for Japan, note that
the pyramid is asymmetrical at the
In this case, the asymmetry results
from the fact that there are many
more females over 80 years of age
than there are males.
This too seems to be typical of
developed nations.
Reasons for the Policy
• China instituted a one child policy in 1979.
• This policy was brought about because of the massive
population growth that China experienced during the 1960s
and 1970s.
• By 1963, the average Chinese woman had given birth to 7.5
• While that rate had dropped to 2.7 births per mother by
1979, there was still great concern about the future
security of the nation’s food supply.
• With 20 percent of the world's population and only 7
percent of the world's arable land, the government
instituted a policy that would ensure that the country
would be able to feed its own people.
China’s Population Structure - 1970
• Here is what the population pyramid for China
looked like in 1970 before the one child policy
was adopted:
This is a typical
population pyramid
for an expanding
Narrowing through
the ages where
most likely to take
Notice the nice
broad base
End of the Policy
• The policy was ended in 2015 after over 30
years of requiring Chinese couples to have
only one child; statistically there are around
150 million families with only one child (⅔ of
all Chinese couples).
• China claims that their one child policy has
averted roughly 400 million births.
Effects of the Policy – Reduced Fertility
• China's country-wide fertility rate dropped to
well below the replacement rate of 2.1
children per woman; decreasing to an
estimated 1.5 children per woman and in
developed urban areas, to an average of one
child per woman.
Effects of the Policy – Reduced Fertility
• To put this number into perspective, the
country of Japan - projected to have a massive
drop in population over the next 40 years - has
the world's fifth lowest total fertility rate
at 1.2 children per woman.
• Macau (a special administrative region of
China) has the world's lowest fertility rate
at 0.91 children per woman.
Effects of the Policy –
Changing Sex Ratio
• The sex ratio among children at birth has
changed from 108 boys for every 100 girls in
1980 to 120 boys for every 100 girls today
resulting in 20 to 30 million excess males.
Effects of the Policy –
Ageing Population
• The number of elderly Chinese aged 65 and
older stood at 144 million in 2007 and is
expected to rise to 391 million by 2035 when
seniors will comprise 25 percent of the total
• The doubling of the number of people over
the age of 65 will take only 27 years, much
faster than the doubling of the number of
seniors in the United States.
Effects of the Policy –
Ageing Population
• Single child families will have to rely on their
sole child to provide for their parents as they
• This will place a social and economic burden
on the next generation as fewer of them will
be required to fund the growing pension,
health care and social welfare benefits of an
increasingly aging population.
Effects of the Policy –
Population Pyramid
• Here is what the population pyramid for China
is projected to look like in 2050:
Notice the following:
The relatively wide top
The narrowing from ages 0 to 19
The narrow base
This is a typical population pyramid
for a contracting population.
Other Effects of the Policy
• Reduced Primary Enrolment:
– Demographic changes have already been noted at the
elementary school level; in 1995, there were 25.3 million
new students enrolled in school. By 2008, that number
had dropped by one-third to 16.7 million.
• Industrial Labour Shortages:
– China is on the cusp of experiencing a decline in new
entrants into its labour force. The days of the seemingly
endless supply of young and cheap Chinese labour is
drawing to a close. The number of young labourers
between the ages of 20 and 29 has already dropped by
14% in the past 10 years and is expected to drop by an
additional 17% in the next 20 years.
Other Effects of the Policy
• Not only will China's demographic changes
have a marked impact on China, it will have a
marked impact on the world's economy.
• Most nations in the world have regarded
China as the world's manufacturer; should a
shortage of labour occur, it will definitely
impact the price of labour resulting in an
impact on prices of goods around the world.
Other Effects of the Policy
• While the rest of the world will be adjusting to
a changing demography as baby boomers
reach their senior years over the next 2
decades, the impact on the world's economy
of that demographic change will be relatively
minor compared to the massive impact felt
when China's massive population reaches the
same point.
• http://www.china-europeusa.com/level_4_data/hum/011_7a.htm
• Brookings Institute: China's One Child Policy at
30 by Feng Wang
• Brookings Institute: China's Population Destiny:
The Looming Crisis by Feng Wang