Demographic Variables (SL IB Environmental Systems & Societies (ESS))

• Demographic tools are essential for understanding and quantifying human population dynamics
  • They provide valuable insights into birth and death rates, fertility patterns, population growth rates, and other demographic indicators

• Below are some key demographic tools and how they are calculated:

Crude Birth Rate (CBR)

• • The CBR is the number of live births per 1 000 individuals in a population during a specific time period
  • It is calculated by dividing the total number of live births in a year by the total population and then multiplying by 1 000

$\mathrm{CBR}=\frac{\mathrm{total} \mathrm{number} \mathrm{of} \mathrm{live} \mathrm{births} \mathrm{per} \mathrm{year}}{\mathrm{total} \mathrm{population}}\times 1 000$

Crude Death Rate (CDR)

• • The CDR is the number of deaths per 1 000 individuals in a population during a specific time period
  • It is calculated by dividing the total number of deaths in a year by the total population and then multiplying by 1 000

$\mathrm{CDR}=\frac{\mathrm{total} \mathrm{number} \mathrm{of} \mathrm{deaths} \mathrm{per} \mathrm{year}}{\mathrm{total} \mathrm{population}}\times 1 000$

Total Fertility Rate (TFR)

• • The TFR is an estimate of the average number of children a woman would have during her reproductive years if she experienced the current age-specific fertility rates throughout her lifetime
  • It is calculated by summing the age-specific fertility rates (ASFR) and multiplying the result by five

$\mathrm{TFR}=\mathrm{\Sigma }\left(\mathrm{ASFR}\right)\times 5$

Doubling Time (DT)

• • The DT is the time it takes for a population to double in size based on its current growth rate
  • It is calculated using the rule of 70, where the number 70 is divided by the population growth rate

$\mathrm{DT}=\frac{70}{\mathrm{growth} \mathrm{rate} \left(\%\right)}$

Natural Increase Rate (NIR)

• • The NIR is the rate at which a population grows or declines due to the difference between the crude birth rate and the crude death rate
  • It is calculated by subtracting the CDR from the CBR and then dividing the result by 10

• These demographic tools provide valuable quantitative measures to analyse and compare population trends across different regions and time periods
• They assist policymakers, researchers, and demographers in understanding population dynamics, projecting future growth, and formulating effective strategies for social and economic development