Demographic transition (DT) is the transition from high birth and death rates to lower birth and death rates as a country or region develops from a pre-industrial to an industrialized economic system.
In stage one, pre-industrial society, death rates and birth rates are high and roughly in balance.
In stage two, that of a developing country, the death rates drop quickly due to improvements in food supply and sanitation, which increase life expectancies and reduce disease.
In stage three, birth rates fall due to various fertility factors such as access to contraception, urbanization. Population growth begins to level off.
During stage four there are both low birth rates and low death rates.
i hope this can help you! i thinks it’s easier to understand if you don’t mind the red line (photo)