Population Estimation

• What is the purpose of population estimates?

  To analyze trends, measure shifts, allocate public funds, and plan.
• What are the measures of changes in population size?

  • Natural increase
  • Rate of natural increase
  • Relative increase
  • Absolute increase per year (b)
  • Annual rate of growth (r)
• How is natural increase defined?

  Natural increase is the number of births minus the number of deaths.
• How is the rate of natural increase calculated?

  It is calculated as crude birth rate (CBR) minus crude death rate (CDR).
• What should you check when calculating the rate of natural increase?

  Ensure that both the crude birth rate and crude death rate are in the same factor.
• If the crude birth rate is 48 per 1000 population and the crude death rate is 2 per 1000 population, what is the rate of natural increase?

  46 per 1000 population.
• How do you adjust the rates if they are in different factors?

  Convert the larger factor to the smaller one before calculating.
• What is relative increase?

  It is the actual difference between two census counts expressed as a percentage of the prior census population size.
• How is relative increase calculated?

  Relative Increase = \(\frac{(P_t - P_0)}{P_0} \times 100\)
• What does \(P_0\) represent in the relative increase formula?

  It represents the population size at the initial time.
• What does \(P_t\) represent in the relative increase formula?

  It represents the population size at time \(t\).
• What is the absolute increase per year (b)?

  It measures the average number of people added to the population per year.
• How is absolute increase per year calculated?

  Absolute Increase = \(\frac{(P_t - P_0)}{t}\)
• Given the population sizes of 92,337,852 in 2010 and 98,393,574 in 2013, what is the relative increase?

  1. 56% increase from 2010 to 2013.
• How do you calculate the time elapsed (t) between two dates for absolute increase?

  Calculate the difference in years, months, and days, then convert to years.
• What is the formula for calculating the annual rate of growth (r)?

  It is calculated using census data to quantify the change in population size.
• What are the methods of estimation for population changes?

  • Component Method: \(P_t = P_0 + (B - D) + (I - O)\)
  • Arithmetic Method: Assumes equal change every year
  • Geometric Method: Assumes constant rate of change
  • Exponential Method: Assumes continuous population growth
• What is the formula for estimating the rate of change (r) using the exponential method?


  r = \(\frac{\ln(P_t / P_0)}{t} \times 100\)
• How do you estimate future population (P_t) using the exponential method?


  P_t = \(P_0 e^{rt}\)
• How do you estimate past population (P_0) using the exponential method?


  P_0 = \(\frac{P_t}{e^{rt}}\)
• What is the formula for estimating the amount of time (t) using the exponential method?


  t = \(\frac{\ln(P_t / P_0)}{r}\)