- A -

Age-dependency ratio
The ratio of persons in the ages defined as dependent on others for support (under 15 years and over 64 years) to persons in the ages defined as economically productive (15-64 years) in a population.


- B -

Baby boom
A dramatic increase in fertility rates and in the number of births during a given period. The United States, Canada, Australia, and New Zealand all experienced a baby boom during the period following World War II.

Baby bust
A rapid decline in fertility rates to unusually low levels.

Birth rate (or crude birth rate)
The number of live births per 1,000 population in a given year.

Brain drain
The emigration of a significant proportion of a country’s highly skilled, highly educated, professional population, usually to other countries offering better economic opportunity. This can create a shortage of, for instance, physicians or technical workers in the sending country.


- C -

Carrying capacity
The maximum sustainable size of a population, taking into account the level of resource consumption and waste discharge that can be maintained indefinitely without impairing the functionality and productivity of the area’s ecosystem.

Census
An official, usually periodic count of a population, often including the collection of related demographic information.

Childbearing years
The reproductive age span of women, assumed for statistical purposes to be 15-44 or 15-49 years of age.

Child-woman ratio
The number of children under age five, per 1,000 women ages 15-44 or 15-49 in a population in a given year. This is a crude fertility measure sometimes used when more specific fertility information is not available.

Contraceptive prevalence
The percentage of couples currently using a contraceptive method.


- D -

Demography
The scientific study of human populations, including their sizes, compositions, distributions, densities, growth, and other characteristics.

Dependency ratio
The ratio of the economically dependent part of the population to the productive part; defined as the ratio of the elderly (ages 65 and older) plus the young (under age 15) to the population in the working ages (ages 15-64).

Domestic migration
The movement of people across a specified boundary within a country for the purpose of establishing a new or semi-permanent residence. In the U.S., generally refers to migration from one state to another.

Doubling time
The number of years required for the population of a given area to double its present size, given the current rate of population growth.


- E -

Ecological footprint
The land and water area that is required to support the material standard of living of a given human population.

Emigration
The process of leaving one country to take up permanent or semi-permanent residence in another.

Emigration rate
The number of emigrants departing an area of origin, per 1,000 population in that area of origin in a given year.


- F -

Family planning
A couple’s effort to regulate the number and spacing of births through artificial and natural methods of contraception.

Fertility
The actual reproductive performance of an individual, a couple, a group, or a population. See general fertility rate.

Finite resources
Resources available only in limited quantity, such as oil and coal. Once they are used, they cannot be replaced.

Foreign-born
People residing in the United States who were born outside the United States. This group includes both legal and illegal immigrants, refugees, students, and temporary workers.


- G -

General fertility rate
The number of live births per 1,000 women ages 15-44 or 15-49 years in a given year.

Growth rate
The percentage by which a population grew in a given year due to natural increase and net migration. Expressed as a percentage of the population at the beginning of the time period.


- H -


- I -

Immigration
The process of entering one country from another to take up permanent or semi-permanent residence.

Industrialized countries
Following the United Nations’ definition, “more developed countries,” or industrialized countries include Europe (including all of Russia), the United States, Canada, Australia, New Zealand, and Japan.

In-migration
The process of entering a country or a part of a country (such as a state) from another country or part of the country.


- J -


- K -


- L -

Less developed countries
Following the United Nations’ definition, the term “less developed countries” refers to countries in Africa, Asia (except Japan), Latin America and the Caribbean, and Oceania (except Australia and New Zealand).

Life expectancy
The average number of additional years a person 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.


- M -

Malthus, Thomas R. (1766-1834)
English clergyman and economist famous for his theory that the world’s population tends to increase faster than the food supply and that unless fertility is reduced, famine, disease, and war must serve as natural population restrictions.

Metropolitan area
A large concentration of population, usually an area with 100,000 or more people. The area typically includes a city with 50,000, as well as the connecting suburbs.

Migration
The movement of people across a specified boundary for the purpose of establishing a new or semi-permanent residence. May refer to international migration (migration between countries) or internal migration (migration within a country).

More developed countries
Following the United Nations’ definitions, “more developed countries,” or industrialized countries include Europe (including all of Russia), the United States, Canada, Australia, New Zealand, and Japan.

Mortality
Deaths as a component of population change.


- N -

Natality
Births as a component of population change.

Natural increase (or decrease)
The surplus (or deficit) of births over deaths in a population in a given time period. Calculated by finding the difference between deaths and births.

Negative population growth
A population growing at a negative rate; achieved when births plus immigration are less than deaths plus emigration.

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.


- O -

Optimum population size
The size a population can attain before the quality of living starts to decline and at which the population as a whole enjoys the highest quality of life.

Out-migration
The process of leaving one subdivision of a country to take up residence in another.

Overpopulation
When area is populated too heavily for the available resources and the capacity of the environment. When an area is overpopulated, its population cannot be maintained without destroying nonrenewable resources and without affecting the capacity of the environment to support current and future inhabitants.


- P -

Population density
Population per unit of land area; for example, persons per square mile.

Population distribution
The patterns of settlement and dispersal of a population.

Population momentum
The lag between reduced fertility and the end of population growth. A population with a large concentration of women in their child-bearing years will continue to increase even if parents do not produce enough children to replace themselves (below-replacement level fertility). This is due to an age distribution with many young people still to have children and a low number of older people.

Population policy
Explicit or implicit measures instituted by a government to influence population size or growth.

Population projection
A computation of future changes in population numbers, given certain assumptions about future trends in the rates of fertility, mortality, and migration. Demographers often issue low, medium, and high projections of the same population, based on different assumptions of how these rates will change in the future.

Population stabilization
Occurs globally when births equal deaths. Occurs on a local or country level when births plus in-migration equals deaths plus out-migration.


- Q -


- R -

Replacement–level fertility
The level of fertility at which a couple has only enough children to replace themselves, or about two children per couple.

Reproductive age
The reproductive age span of women, assumed for statistical purposes to be 15-44 or 15-49 years of age.


- S -

Smart Growth
Efforts by a community to direct population growth and development into specific areas, usually intended to shift development from outside the city limits to within the city core, in order to preserve green space, save farmland, and reduce commuting distances. However, this type of growth management results in higher densities and doesn't tackle the problem (population growth) directly.

Sprawl
Dispersed development outside of compact urban and village centers along highways and in rural countryside. Sprawl is typically characterized by significant land consumption, low average densities in comparison with older centers, automobile dependence, and fragmented open space.

Stable population
A population with an unchanging rate of growth and an unchanging age composition as a result of age-specific birth and death rates that have remained constant over a sufficient period of time.

Sustainability
Successfully meeting the needs of the present population without limiting the ability of future generations to meet their own needs.


- T -

Total fertility rate (TFR)
The average number of children that would be born to a woman during her lifetime if she were to pass through her childbearing years bearing children at the age-specific fertility rates of a given year.


- U -

Urban
In the U.S., the Census Bureau defines “urban” as territory consisting of core blocks that have a population density of at least 1,000 people per square mile and surrounding blocks that have an overall density of at least 500 people per square mile.

Urbanization
Growth in the proportion of a population living in urban areas.


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- W -


- X -


- Y -


- Z -

Zero population growth
A population in equilibrium, with a growth rate of zero, achieved when births plus immigration equal deaths plus emigration.