How does the Demographic Transition Model explain the relationship between economic development and population age structure?

The Demographic Transition Model (DTM) explains how a country's population changes as it develops economically. It shows that as countries grow and improve their economy, they typically move through four stages. In the first stage, both birth and death rates are high, so the population grows slowly. As the country develops, the death rate drops due to better healthcare and living conditions, while birth rates begin to decline, leading to a younger population. For example, in a developing country like India, you can see a shift where more people are living longer, and families are having fewer children, which changes the age structure over time.