China has far fewer children: There are "only" some 237 million children aged 0 to 14.
Would you have guessed that Nigeria - not Indonesia - has the third largest population of children? There are more than 80 million children age 0 to 14 in Nigeria.
In 2015, more than half of the population in Niger were children under the age of 15
Most other African countries also have a very high percentages of children in their population. For instance, in Uganda, Chad, Angola and Mali the proportion of children in the population ist more than 47%.