Demography - Population Composition: Age Structure Flashcards
Demographers’ definition of age
Completed age, i.e. age of an individual at last birthday (i.e. disregarding fractions of days and months)
Most important variable in demographic analyses
Define Age structure
- A summary of the number of individuals of each age in the population
- Provides the distribution of the population according to age
- A normal age structure begins with a large number of persons in the first age group, gradually diminishes in subsequent age groups until the final age group at around 100 when the number becomes zero
Types of age structure (Three main types)
Progressive: Population having a high proportion of children and small number of elderly,
– characterized by a high birth rate, high death rate and high growth rate
Stationary: Population having a moderate proportion of children and aged persons,
– characterized by a low birth rate, low death rate and slow growth rate
Regressive: Population having a high proportion of aged persons and declining numbers
– characterized by a low birth rate, and low death rate
Describe the population pyramid
- Gives a detailed picture of the age-sex structure of a population
- Consists of bars representing age groups in ascending order from lowest to highest pyramided on one another
- Age is located on the vertical axis and the totals of each age group on the horizontal axis
- Bars are generally by single or 5-year age groups
Continued description of population pyramid - Number, Gender, Percent
- Number (or percentage) of persons in an age group is indicated by length of its bar from central axis
- Males on left side; females on right side
- Pyramids with absolute numbers show differences in overall sizes of total populations and in number at each age
- Percent pyramids show relative differences in population size at each age-sex group
Description of Population pyramid - shape
- Pyramids are of different shapes determined by fertility, mortality and migration factors
- Each rectangle representing an age group has a length that depends on; the totals at birth, amount of reduction by mortality, and the amount of migration
- Three main types:
Broad base
Barrel shape and
Irregular shape
Broad based pyramid
- Pyramid narrows rapidly from the base upwards and generally triangular in shape
- Suggests a population with high birth rate and high death rate and a high growth rate
- Shows progressive population structure typical of developing countries
Barrel shaped pyramids
- There is moderate proportion of children and aged persons
- Suggests a population with low fertility and low mortality rates and slow growth rate
- Typical of developed countries
Irregular shaaped pyramids
Points to sharp fluctuation in;
– Number of births
– Volume of migration
– Temporary rise in deaths resulting from wars and epidemics
Define median age. What do the median ages of Ghana represent
- Age above which half of the population lies and below which lies the other half of the population
- Median ages of Ghana are suggestive of the youthfulness of the population resulting from high birth rate. Eg the median age in 2000 was 18.4 years compared to 36.7years & 35.7 years for Canada & USA respectively
Comparethe population pyramids of Ghana & UK
8 Ghana’s population is broad-based with 43.1% of the population under 15years as compared to 19.2% for the UK
– The youthful age structure presents a high potential for rapid population growth as well as high dependency burden
- In developed countries about two active persons support one dependent person, in Ghana one active person support one dependent
- The population 65 years and above stands at 5.3% for Ghana as compared with 15.8% for the UK
What are the demographic implications of age structure?
- More births have effect on death rate as the care of children is lowered
- Experience of death rate may relatively encourage high fertility
- A bulge in age structure at the youth adult tend to raise birth rate
- Young age structure produced by high fertility encourages relatively large number of migrants
What are the socio-economic (household level) implications of age structure
- High number of children in the household means high expenditure on education, food, clothing, etc
- There is little savings and may result in poverty where children may be forced to work to supplement household income
- May result in their neglect with subsequent high mortality rate
Define age dependency ratio. What do high and low ratios mean?
Give an example of age dependency ratio
- Age dependency ratio is the ratio of dependent-age population (the young and the old) to working age population
- The higher the ratio, the more people each potential worker has to support
- The lower the ratio, the fewer the dependents
- In 2000, the dependency ratios for Ghana & Canada were 89.9% & 47% respectively: Meaning 1 working age person supporting 1 dependent in Ghana & 2 working age persons supporting 1 dependent in Canada
Brief history of age structure of Ghana’s population
- In 1984, 45% were < 15 years, decreased to 41.9% in 2000 & decreased further to 38.3% in 2010
- The median ages have increased from 17.5 years in 1984, through 18.9 years in 2000 to 20 years in 2010
- The dependency ratios have decreased from 96%, 89.4% to 75.7% from 1984, through 2000 to 2010
