The document describes the four stages of the demographic transition model: Stage 1 - Both birth and death rates are high due to diseases, famine, lack of infrastructure. Stage 2 - The death rate begins to fall due to improvements in sanitation and medicine. The birth rate remains high due to social and economic factors. Population growth is rapid. Stage 3 - The birth rate starts to fall due to increased access to family planning, fewer child deaths, urbanization, and social/economic changes. Population growth slows. Stage 4 - Both birth and death rates are low, resulting in low population growth or steady population levels, as seen in developed nations today.