Population Size

• Four main factors that affect  population size
• Birth rate
• Death rate
• Immigration
• Emigration

• The measures of population change are
• Crude birth rate (CBR)
• The Crude Birth Rate (CBR) includes the number of births per 1000 individuals. So, the formula for this is:

• CBR = (Number of births / population size) x 1000
• The CBR in the world is 20.3 per 1000 per year.
• Crude death rate
• The number of deaths per 1000 individuals in a population per year
• Calculated by dividing the number of deaths by the size of population and multiplied by 1000
• Doubling rate
• The time in years that it takes a population to double its size
• Doubling time = 70/NIR
• Natural increase rate
• NIR=(CBR-CDR) / 10
• This gives NIR on %
• Does not consider immigration or emigration
• Total Fertility Rate
• The average number of children that each woman has over her lifetime. It shows the potential for population change in a country.
• A TRF > 2.0 results in a population increase
• A TRF < 2.0 results in a population decrease
• A TRF = 2.0 results in a stable population