What is the definition of demographic transition?

Demographic transition refers to the shift in a population's dynamics over time, typically marked by changes in birth and death rates as a country develops economically. This transition often involves several stages, starting with high birth and death rates, moving to lower death rates with continued high birth rates, and eventually leading to low birth and death rates as a society becomes more urbanized and industrialized. This framework helps in understanding how populations grow and change in response to various socioeconomic factors.

The other options do not encompass the broader concept of demographic transition. A single migration event pertains to the movements of people and does not reflect changes in overall population dynamics over time. The impact of education on fertility rates is an important topic within demographic studies but is just one aspect of the larger transition process. The relative size of different age groups reflects a population's structure at a specific time and does not capture the temporal aspect of the changes occurring during demographic transition. Thus, the definition of demographic transition includes the gradual and significant shifts in population characteristics over time, making the second option the most accurate response.