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