Echo boomers
The generation of Americans born between 1977 and 1994.
Baby boomers
The generation of Americans born between 1946 and 1964.
Demography
The study of the basic population processes of fertility, mortality and migration.
Age structure
The distribution of people across various age cohorts.
Population aging
Occurs when the portion of older people relative to younger generations increases; a term that refers to an increase in the proportion of people 65 or older.
Life span
The longest number of years any member of a species has been known to survive.
Life expectancy
The average number of years people in a given population can expect to live; the mean age at death; a measure of the combined outcome of many births and deaths calculated by taking the sum of the ages of death of all individuals in a given population and dividing it by the number of people in that population.
Sex ratio
The ratio of males to females; determined by the number of males relative to females at birth and by different survival rates over the life course.
Fertility rate
A measure of the incidents of births or the inflow of new lives into a population.
Mortality rate
The incidence of death in a population.
Migration
The movement of people across borders.
Population pyramid
A bar chart that reflects the distribution of a population by age and sex.
Demographic transition
The shift from high mortality and fertility to low mortality and fertility that causes population aging; occurs in three stages.
Elderly dependency ratio
The number of persons age 65 or older per 100 persons of working age.
Child dependency ratio
The number of persons younger than 18 relative to those of working age.
Total dependency ratio
The combined ratio of children and older people to workers.
Race crossover
Among the oldest-old, the mortality rate for African Americans falls below that of whites.