How does the demographic transition explain trends in past world population growth?

The demographic transition model explains past world population growth through four stages: pre-industrial, transitional, industrial, and post-industrial. In the pre-industrial stage, high birth and death rates result in stable population levels. As societies transition to the next stages, improved healthcare and sanitation reduce death rates, while birth rates remain high, leading to rapid population growth. Eventually, as countries industrialize and urbanize, birth rates decline, stabilizing the population as seen in more developed nations today.