Population Glossary
Age-sex structure
The composition of a population as determined by the number or
proportion of males and females in each age category. The age-sex
structure of a population is the cumulative result of past trends in
fertility, mortality, and migration. Information on age-sex composition
is essential for the description and analysis of many other types of
demographic data.
Baby boom
A dramatic increase in fertility rates and in the absolute number of
births. In the United States this occured during the period following
World War II (1946-1964).
Birth rate (or crude birth rate)
The number of live births per 1,000 population in a given year. Not to
be confused with the growth rate.
Death rate (or crude death rate)
The number of deaths per 1,000 population in a given year.
Growth rate
The number of persons added to (or subtracted from) a population in a
year due to natural increase and net migration; expressed as a
percentage of the population at the beginning of the time period.
Less developed countries
Less developed countries include all countries in Africa, Asia
(excluding Japan), and Latin America and the Caribbean, and the regions
of Melanesia, Micronesia, and Polynesia.
Life expectancy
The average number of additional years a person of a given age could
expect to live if current mortality trends were to continue for the rest
of that person's life. Most commonly cited as life expectancy at birth.
More developed countries
More developed countries include all countries in Europe, North
America, Australia, New Zealand, and Japan.
Mortality
Deaths as a component of population change.
Net migration
The net effect of immigration and emigration on an area's population in
a given time period, expressed as an increase or decrease.
Population pyramid
A bar chart, arranged vertically, that shows the distribution of a
population by age and sex. By convention, the younger ages are at the
bottom, with males on the left and females on the right.
Rate of natural increase
The rate at which a population is increasing (or decreasing) in a given
year due to a surplus (or deficit) of births over deaths, expressed as a
percentage of the base population.
Zero population growth
A population in equilibrium, with a growth rate of zero, achieved when
births plus immigration equal deaths plus emigration. Zero growth is not
to be confused with replacement level fertility.