Population Clock
Population Models
3.1.1 Describe the nature and discuss the implications of exponential human population growth
3.1.2 Calculate and explain from given data the values of crude birth rate, crude death rate, fertility, doubling time, and natural increase rate.
3.1.3 analyse age sex pyramids showing demographic transition models
3.1.4 discuss the use of models in predicting the growth of human populations

Population changes
Changes in population size occur through births, deaths, immigration and emigration.
The factors affecting global human population are very simple: They are birthrate, mortality, initial population, and time.

Population Terms
 Crude death rate, CDR: The number of deaths per 1000 people.
 Crude birth rate, CBR: The number of births per 1000 people.
 Natural rate of increase = Percent rate of increase

Rate of natural increase calculations
How rapidly a population grows depends upon the difference between the crude birth rate
(CBR) and the crude death rate (CDR).
Natural Rate of increase, NIR is a percentage.
NIR = CBR - CDR
10

Calculate the NIR for the following countries: country
Uganda
Pakistan
Chile
China
47
30
15
12
Crude birth rate (CBR)
Crude
Death Rate
(CDR)
Natural
Rate of
Increase,
NIR (%)
6
7
13
7

Natural rate of increase, % country
Uganda
Pakistan
Chile
China
Crude birth rate (CBR)
Crude
Death Rate
(CDR)
47
30
15
12
13
7
6
7
Natural
Rate of
Increase,
NIR (%)
3.4 %
2.3 %
0.9 %
0.5%

Doubling time
 One of the simplest approaches to making population projections is to calculate doubling time.
 The doubling time is the length of time required for a population to double in size.
 Rule of 72 = 72/NIR = Doubling time

Calculate the Doubling time for each of the following countries country
Uganda
Pakistan
Chile
China
Natural Rate of increase,
NIR %
3.4 %
2.3%
0.9%
0.5%
Doubling
Time / Years

Doubling time: The time it takes the population to double its size country
Uganda
Pakistan
Chile
China
Natural Rate of increase,
NIR %
3.4 %
2.3%
0.9%
0.5%
Doubling
Time / Years
21
33
80
144

Calculate the NIR and doubling time for the world
 The crude birth rate, CBR, is 20 births per
1000 population
 The crude death rate, CDR, is 8 deaths per 1000 population
 Calculate NIR and doubling time for the human population!

Based on the previous data..
 1.2 % increase
 Doubling time = 60 years
 So, if the NIR does not change, the world population will double from 7 billion to 14 million by 2072!

Can be Changed
Cannot be Changed
Population Changes
Birthrate Mortality Initial population Time.
Affected by…

Fertility http://www.ined.fr/en/everything_about_pop ulation/animations/fecondity/

Total Fertility Rate, TFR
 The average number of children that a woman will have in her lifetime.
Uganda: 6.5 children per woman
Zimbawe: 3.8 children per woman
Chile: 1.9
China: 1.5
Japan: 1.4
World average: 2.6

http://www.census.gov/population/international/ data/worldpop/table_population.php

Replacement-level Fertility
 Replacement -level fertility is the number of children that a couple must have to replace themselves.
2.1 in MECD ’s
2.5 in some LEDC ’s

Useful indicators of the health of a country
Life expectancy: The average number of years that a newborn infant can expect to live.
Infant mortality rate, IMR: The number of babies out of 1000 born that die before their first birthday.
High infant mortality rate usually indicates malnutrition, disease from contaminated drinking water, poor prenatal care, few doctors at births.

Life
Expectancy http://www.ined.fr/en/everythin g_about_population/animations/ life_expectancy/

Infant Mortality Rate, IMR
 The number of children who die before their first birthday per 1000 live births.
 Uganda: 76
 USA: 6.4
 Chile: 8.3
 China: 21.0
 Japan: 2.1

Average Life expectancy
 The average number of years a person is expected to live.
 Afghanistan: 43 years
 China: 74 years
 Chile: 79 years
 USA: 78 years
 Japan: 82 years

Mortality
In MEDC ’ s, the death rate has dropped, more or less continuously, since the start of the industrial revolution.
In LEDC ’ s CDR have also decreased, but at rates lower than in
MEDC ’ s.

More about Mortality
 The downward trend of the death rate is common to most countries.
Personal hygiene
Improved methods of sanitation
Modern medicine
Antibiotics
Vaccinations
Improved Food Supply