Human Populations
Inputs and Outputs of Human Population
Inputs:
- Births: The arrival of new individuals in the population through reproduction.
- Immigration: Movement of individuals into a population from other regions or countries.
Outputs:
- Deaths: The number of individuals who die in a population.
- Emigration: Movement of individuals out of a population to other areas or countries.
Population Dynamics and Its Calculation
Population dynamics is the study of changes in population size and structure over time, influenced by birth rates, death rates, immigration, and emigration.
Total Fertility Rate (TFR)
The Total Fertility Rate represents the average number of children a woman would have over her lifetime if current age-specific fertility rates remained constant. It's a more refined measure than CBR as it accounts for age structure.
NoteA TFR of about 2.1 is considered the replacement level in developed countries, meaning the population would remain stable (not accounting for migration).
Doubling Time (DT)
Doubling Time is the period required for a population to double in size, assuming a constant growth rate. It's calculated using the "Rule of 70":
π·π= 70/Annual growth rate (%)
ExampleIf a population has a 2% annual growth rate, its doubling time would be:
π·π = 70/2 = 35 years
Natural Increase Rate (NIR)
The Natural Increase Rate is the difference between the birth rate and death rate, expressed as a percentage:
ππΌπ =(πΆπ΅π βπΆπ·π )Γ·10
TipRemember that NIR doesn't account for migration, which can significantly affect population change in some regions.
Population models
The global human population has followed a rapid growth curve. Models are used to predict the growth of the future global human population.
