If annual growth rate of population is 1.2%, the population is likely to get doubled in:

Rate Annual GR % Yrs required Stationary No growth - Slow growth 0.5 >139 Moderate growth 0.5-1 139-70 Rapid growth 1-1.5 70-47 Very rapid growth 1.5-2 47-35 Explosive growth 2-2.5 35-28 Explosive growth 3-3.5 23-20 Explosive growth 3.5-4 20-18