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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 Clock
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 Crude birth rate (CBR)
Crude Death Rate (CDR)
Natural Rate of Increase, NIR (%)
Uganda 47 13
Pakistan 30 7
Chile 15 6
China 12 7
Natural rate of increase, %
country Crude birth rate (CBR)
Crude Death Rate (CDR)
Natural Rate of Increase, NIR (%)
Uganda 47 13 3.4 %
Pakistan 30 7 2.3 %
Chile 15 6 0.9 %
China 12 7 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 Natural Rate of increase, NIR %
Doubling Time / Years
Uganda 3.4 %
Pakistan 2.3%
Chile 0.9%
China 0.5%
Doubling time: The time it takes the population to
double its sizecountry Natural
Rate of increase, NIR %
Doubling Time / Years
Uganda 3.4 % 21
Pakistan 2.3% 33
Chile 0.9% 80
China 0.5% 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!
Population Changes Birthrate Mortality Initial population Time.
Can be ChangedCannot be Changed
Affected by…
Fertility
http://www.ined.fr/en/everything_about_population/animations/fecondity/
Total Fertility Rate, TFR The average number of children that
a woman will have in her lifetime.
Uganda: 6.5 children per womanZimbawe: 3.8 children per womanChile: 1.9China: 1.5Japan: 1.4World average: 2.6
2008 values from Population Reference Bureeau
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 Expectanc
y
http://www.ined.fr/en/everything_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 hygieneImproved methods of sanitation Modern medicine Antibiotics VaccinationsImproved Food Supply