Formulas and ratios to measure the changes

There are 4 main factors affecting population change:

• Birthds
• Deaths
• Immigration
• Emigration 

And to measure changes in those, we use:

• Crude birth rate: Number of births per 1000 individuals. Dividing the number of births by population size.

CBR= (# of births/ total population) * 1000

• Crude death rate: doesn’t includes anything else but # of dead. Number of deaths per 1000 individuals. 

CDR= ( # of deaths/total population) * 1000

• Natural increase rate: Doesn't consider immigration/emigration. Gives a percentage of growth.

NIR= (CBR-CDR)/10

• Doubling rate: How fast a particular population doubles its amount.

Doubling time= 70/ NIR

• Total fertility rate: the average number of children that each woman has over her lifetime, it shows the potential for population change.

·         TFR=2.0 population is stable.

·         TFR < 2.0 population decrease.

·         TFR >2.0 population increase