Why is doubling time so low in African countries?

Answer 1

Doubling of what??

Answer 2

doubling time is the time it takes for a country's population to double in number

Answer 3

According to the statistics in this site, Africa doesn't have an especially low doubling rate.

http://en.wikipedia.org/wiki/World_population

However, high death rates and lack of immigration probably keep its population increase lower than some other places.