Population change

Demographic transition

• Historical shift of a population from high birth and death rates to low birth and death rates as a society modernises and develops economically.

• Demographic (people) transition (change)

Natural Increase

• Calculated by subtracting the crude death rate from the crude birth rate

• Expressed as a percentage

• Occurs when the death rate exceeds the birth rate

• Does not take migration into account

• It is rare for a country’s NI to exceed 3% per annum (year)

Population change

• The balance between birth rate, death rate and migration

• Recorded as net change per 1000 people or as a percentage.

Population momentum

• The tendency for a population to grow despite a fall in the birth rate or fertility levels.

• Occurs because of a relatively high concentration of people in the pre-childbearing and childbearing years

• As these young people grow older and move through their reproductive years, the greater number of births will exceed the number of deaths in the older populations, and so the population will continue to grow.

Example:

• If a country used to have a total fertility rate of 5 —> better health care means that more babies survive childhood, creating a large group of children and teenagers (“youth bulge”).

• Suddenly, social changes and family planning cause the fertility rate to drop to 2 children per couple

• Even though people are now having fewer children, the large generation of children will soon enter their reproductive years (15-49). Because there are many potential parents, the total number of births remains high

• The total population continues to grow for several decades, until the young generation moves past childbearing age and the age structure balances out.

Total Fertility Rate

• Average number of children a woman gives birth to during her lifetime

• Highest fertility rates are found among the poorest countries

• Although some LICs have made the transition from high fertility rates to low fertility rates

• Most HICs by contrast, experience much reduced fertility rates

• Eg. TFR of 2.1 = hypothetical woman has an average of 2.1 children in her lifetime = “replacement level” to keep a population stable

General Fertility Rate

• Number of live births in a specific year divided by the total number of women of childbearing age (typically ages 15-44/49).

• Expressed as the number of births per 1,000 women in that age group per year

• Eg. Fertility rate of 62.5 means there are 62.5 births for every 1,000 women of reproductive age in that calendar year

Life expectancy

• Average number of years that a person can be expected to live, usually from birth, assuming that demographic factors remain unchanged

• Varies from over 80 years in a number of developed countries such as Monaco, Japan, Singapore and Macau to under 50 years for men in Chad

Population structure

• Composition of a population, usually defined by the distribution of people against different age groups and genders

• Youth: 0-14

• Working Age: 15-64

• Elderly: 65+

Dependency ratio

Metric which compares the non-working age population (dependents) to the working-age population.

Working age group: 15-64

Dependent group: 0-14, 65+

Low ratio = more workers support fewer dependents, which eases pressure on healthcare, pensions and public services

High ratio = higher financial and tax burden on the working population to fund social support systems.

Crude Birth Rate - CBR

• Number of live births per 1,000 people per year in a region.

• In pre-industrial societies the CBR is around 45 births per 1,000 per year.

• The European average is around 11 births per 1,000 per year.

Crude Death Rate (CDR)

• Number of deaths per 1,000 people per year in a region.

• In pre-industrial societies the rate is around 40-50 deaths per 1,000 per year.

• Today the European average is 10 deaths per 1,000 per year.

• The CDR can greatly increase due to disasters/disease

• The CDR in Haiti went from 8 per 1,000 to 32 deaths per 1,000 in 2010, in account of a large earthquake

Infant Morality