Demographic Transition: The process of change in a society's population structure from high birth rates and death rates to low birth rates and death rates.
Age Dependency Ratio: The ratio between the economically dependent age group (typically younger than 15 or older than 64) and the working-age population.
Baby Boomers: People born during a period of increased birth rates after World War II, leading to significant shifts in population structure as they reached old age.