Life table and migration

A life table follows a hypothetical cohort of newborns through life under current age-specific death rates, showing how many survive to each age and how long they can expect to live. From it comes life expectancy — the average remaining years — the single most compact summary of a population's mortality. Migration is the other flow reshaping populations: people move within countries (rural to urban) and across borders, driven by push factors (unemployment, conflict, disaster) and pull factors (jobs, wages, services). Worked example: in a life table starting with 100,000 newborns, if 2000 die in the first year, the infant death probability q0 is 2000/100,000 = 0.02, and 98,000 survive to age 1.