Why is the population growing mainly in underdeveloped countries?

example in the Russian village a couple of hundred years ago.
1) gave birth to many children due to the fact that many of them died, that is, there is no medicine in underdeveloped countries.
2) gave birth in order to help with the household, that is, additional labor in the family



One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.