the average age that a person in a given population can
expect to live to.it varies from one country to another.
life expectancy:
the average number of children a woman in a given
population will have in her lifetime. This number is different in
different countries.
total fertility rate:
the total fertility rate needed for a population to replace
itself. This number varies by country, but is about 2.1 in most
developed countries.
replacement rate:
the study of human populations, including how they change due to births, deaths, aging, and migration
demography:
the number of old and young dependents who don’t work compared with the working-age population. The higher the ratio, the more young and old people the workers have to support.