The "big difference in birthrate": in the early stages of development of human history, the birth rate is relatively high due to the need to maintain the race and demand for productive forces for the development of the commune. At the same time, the death rate is also relatively high due to limited living conditions, natural disasters, epidemics, etc. Therefore, during this period birth and death rates are relatively balanced. In contrast, during the "population boom" the birth rate continued to be maintained while the mortality rate tended to decrease due to improved living conditions, along with the strong development of science Basic human needs are emphasized especially in hygiene and health, leading to a reduction in mortality. In addition, the life expectancy of people has been gradually improved. In 1975, the average age of the world population was 21.9 years, and by 2000 it was 26.6 years.
- Demand for "productive forces": in underdeveloped countries with high labor demand
- Perception backward: In some countries, especially in the East countries, there are some backward concepts: multiple births, male thoughts, male descent