Final answer:
Demographers use the "push-pull theory" to explain the reasons for immigration, which includes push factors driving people away from their home countries, and pull factors that attract them to a new country. The study of these factors helps to understand migration patterns and their effects on population dynamics.
Step-by-step explanation:
Demographers use the "push-pull theory" to explain the reasons for immigration. This theory describes how various factors influence the migration of individuals and populations. Push factors are those that compel people to leave their country of origin, such as political instability, economic hardships, wars, and environmental disasters. On the other hand, pull factors are attractive features of a destination country that draw immigrants, like job opportunities, political stability, and a better quality of life. Demographers study these factors to understand migration patterns and the impacts on both the origin and destination countries.
Migration, including immigration and emigration, is a significant factor that impacts population dynamics, along with birthrates and mortality rates. The routes and flows of human migration are also affected by various political, economic, social, and environmental conditions as well as physical geography. Demographers and sociologists study these trends and patterns to forecast population growth and its potential outcomes on society and natural resources.