1. Age Structure – Demographic Transition

2. Malthusian Theory
Thomas Malthus wrote An essay on the principles of population in 1798
Pessimistic
Claimed food supply was the main limit to population size
Believed that population growth is exponential , but food production is linear
Some “neo-malthusians” believe we are starting to see these limits now

3. Boserup’s Theory Ester Boserup 1965
Population growth will stimulate technology to increase food supply
“Necessity is the mother on invention”
Population growth naturally leads to development
Difficult to “test” due to migration

4. Why do people have large families?
High infant/childhood mortality
Have more than you need to be sure some will make it to adulthood
Security in old age
Children take care of their parents
Children are an economic asset
Especially in agricultural societies
Status of women
In many countries women are deprived of rights such as property, career, education
Instead they make children
Unavailability of Contraceptives
In LEDCs many women would like to have them, but cannot get them

5. Age structure diagram (Also called age-sex histogram or population pyramids)
Usually broken into three categories
Prereproductive 0-14 
Reproductive 
Post reproductive 45-dead 
The shape of the age structure diagram is useful in determining future growth

6. Rapid Growth Slow Growth
Male
Female
Male
Female
Rapid Growth
Guatemala
Nigeria
Saudi Arabia
Slow Growth
United States
Australia
Canada
Ages 0-14
Ages 15-44
Ages

7. Zero Growth Negative Growth
Male
Female
Male
Female
Zero Growth
Spain
Austria
Greece
Negative Growth
Germany
Japan
Sweden
Ages 0-14
Ages 15-44
Ages
Video Link

8. POPULATION AGE STRUCTURE UNITED STATES
What do the yellow bars, moving up the diagram represent?
Look at the last structure on the right. What is odd about it?
What are the consequences of an aging population?

9. The Demographic Transition
As countries become industrialized their death rates decrease and their population grows
Later their birth rates decrease, and the population stabilizes

10. Model of Demographic Transition
Some developing countries may have difficulty making the demographic transition.
Demographic trap: Stuck in transition, pop. growth overwhelms economic growth
Insufficient capital to move into next stage.

11. In the transitional stage, which decreases first?
Birth or death rates?

12. Demographic transition
Stage 1: High Stationary (pre industrial)
Stable population – high birth/death rate
Poor living conditions (disease, famine etc.)
Low per capita income
Poor sanitation
High infant mortality
Low use of birth control

13. Demographic transition
Stage 2: Early Expanding (Early Transitional)
Increased food supply
Better sanitation/healthcare
Death rate drops, life expectancy increases
Infant mortality drops sharply
Birth rate still high
Population grows rapidly (2.5-3% a year)

14. Demographic transition
Stage 3: Late Expanding (Late Transitional)
Industrialization (development) continues
Birth rates start to fall thanks to
contraception, emancipation of women, education
Infant mortality drops sharply
Population growth starts to slow and families become smaller

15. Demographic transition
Stage 4: Low Stationary (Industrial)
Industrialization is widespread
Per capita income is up
Birthrate decreases sharply
Birth rate approaches death rate
Slow to no population growth 
Most developed countries are in this phase

16. Demographic transition
Stage 5: Declining (Postindustrial)
Populations may not be replaced
Fertility rate is low
Problems of an aging workforce
85% of the world has yet to reach this stage
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17. Demographic transition and age structure