Doubling Time

Doubling time is calculated by 72 divided by the rate of growth (r).

$$72/r$$

Fertility rate: measures x children being born to women between 15 and 45 years of age.

Productive sector: between ages of 18 and 65 in first world, and between 10 and 45 in the fourth and fifth worlds.

Growth Rate: (Immigration - Emmigration) + (Birth Rate - Death Rate)

Example: 5.6% Immigration

2.3% Emmigration

4.9% Birth Rate

3% Death Rate

Migration rate: 5.6% - 2.3% = 3.3%

Natural increase: 4.9% - 3% = 1.9%

Growth rate: 3.3% + 1.9% = 5.2%

72/5.2 = 13.88 = ~14 years