Updated: 16 May, 2003
www.ecofuture.org/pop/terms.html

 
 

Population Terms and Definitions


EcoFuture ™

 
Glossary of Population Terms, from Population Reference Bureau. From Population Handbook - A Quick Guide for Journalists, Teachers, etc., 70-page booklet, ISBN 0-917136-09-8. It contains definitions and features "Calculating the TFR", "How Life TablesWork", etc.
 
Also see the Glossary of Population Terms from Institut National d'etudes Demographiques (INED).
 
Selected terms from these and other glossaries include:
 
 
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.
 
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.
 
Carrying Capacity: The maximum sustainable size of a resident population in a given ecosystem.
 
Crude birth rate: The number of births in a given year divided by the total population in that year.
 
Demographic Transition: (1) The historical shift of birth and death rates from high to low levels in a population. The decline of mortality usually precedes the decline in fertility, thus resulting in rapid population growth during the transition period. (2) The transition from a traditional demographic regime in which fertility and mortality are high to a modern regime in which fertility and mortality are much lower. The transition from a so-called regime of "natural" fertility (not controlled by couples) towards a regime of "controlled" fertility may be referred to as a fertility transition. The period during which mortality decreases is referred to as an epidemiological transition or a health transition. It is accompanied by improved health, nutrition and organization of health services and a change in the causes of death, infectious diseases disappearing progressively in favor of chronic and degenerative diseases and accidents.
 
Doubling time: The number of years required for the population of an area to double its present size, given the current rate of population growth. Population doubling time is useful to demonstrate the long-term effect of a growth rate, but should not be used to project population size. Many more developed countries have very low growth rates and, as a result, the equation shows doubling times of hundreds or thousands of years. But these countries are not expected to ever double again. Most, in fact, likely have population declines in their future. Many less developed countries have high growth rates that are associated with short doubling times, but are expected to grow more slowly as birth rates are expected to continue to decline. [Note that the U.S. is projected to double. Also see explanation and examples].
 
Fecundity: The physiological capacity of a woman to produce a child.
 
Fertility: (1) The actual reproductive performance of an individual, a couple, a group, or a population. See general fertility rate. (2) The term fertility is used instead of natality when births are put in relation with the number of women of fertile age. The fertility of a generation can be summarized by completed fertility and mean age at childbirth, whereas the total period fertility rate measures the fertility rate for the year.
 
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 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. (Also see World Bank Population Growth Rate information).
 
Immigration Rate: The number of immigrants arriving at a destination per 1,000 population at that destination in a given year.
 
Life Expectancy at Birth: The average number of years a newborn infant would be expected to live if health and living conditions at the time of its birth remained the same throughout its life. (Also see World Bank Life Expectancy information).
 
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.
 
More developed countries: More developed countries include all countries in Europe, North America, Australia, New Zealand, and Japan.
 
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.
 
Mortality: Deaths as a component of population change.
 
Natural Increase (or Decrease): The surplus (or deficit) of births over deaths in a population in a year or given time period.
 
Net Migration Rate: The net effect of immigration and emigration on an area's population, expressed as an increase or decrease per 1,000 population of the area in a given year.
 
Population Increase: The total population increase resulting from the interaction of births, deaths, and migration in a population in a given period of time.
 
Population Momentum: The tendency for population growth to continue beyond the time that replacement-level fertility has been achieved because of the relatively high concentration of people in the childbearing years. (Also see momentum factors and decreasing population momentum.)
 
Population Policy: Explicit or implicit measures instituted by a government to influence population size, growth, distribution, or composition.
 
Population Projection: 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 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: A ratio between events having occurred in a population during a year and the number of persons in a population in the middle of the year. When the events are observed over a period shorter or longer than a year their number is multiplied or divided by the appropriate factor so as to preserve the rate's annual dimension. A rate may refer to all of the population (mortality rate, birth rate, etc), or to an age or age group (age-specific mortality rate, or age-specific fertility rate).
 
Rate of Natural Increase (or Decrease): 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.
 
Replacement-Level Fertility: The level of fertility at which a couple has only enough children to replace themselves, or about two children per couple. [2.1 children per woman in the U.S.]
 
Total Fertility Rate (TFR): (1) The average number of children that would be born alive to a woman (or group of women) during her lifetime if she were to pass through her childbearing years conforming to the age-specific fertility rates of a given year. This rate is sometimes stated as the number of children women are having today. See also gross reproduction rate and net reproduction rate. (2) An estimate of the average number of children that would be born to each woman if the current age-specific birth rates remained constant. (2) A hypothetical estimate of completed fertility. It indicates how many births a woman would have by the end of her reproductive life, if, for all of her childbearing years, she was to experience the age-specific birth rates for that given year. (From U.S. Census Bureau Fertility of American Women: June 2000).
 
Zero population growth: A population in equilibrium, with a growth rate of zero, achieved when births plus immigration equal deaths plus emigration.
 
 
 
 
 

Population Terminology - Quick Reference
 
Courtesy Janet Braithwaite. Based on The Population Reference Bureau's Population Handbook, International Edition. Reprinted with permission.
 
Indicator
Description
Formula

Age and Sex Composition
Median Age Exactly ½ is older and ½ is younger  
Sex Ratio Males:100 Females in a given year # males/# females * K
Age-Dependency Ratio Dependent population: economically productive in a given year (< 15 + > 64)/ 15 > Pop <64 * K

Fertility
Parity The number of children previously born alive to a woman.  
Birth Rate (Crude Birth Rate) #live births per 1000 population in a given year # live births/ total population * K
General Fertility Rate (Fertility Rate) #live births per 1000 women ages 15-49 in a given year
(US: ages 15- 44)
# live births/ 15 > women < 49 * 1000
Age-Specific Fertility Rates # live births to specific age group/# of women in that age group in a given year # live births to specific age group/# of women in that age group
Completed Fertility Rate # of "children ever born" to women > 49 total # live births to women >49/#women >49 * K
Total Fertility Rate (TFR) Average # of live births that would be born to a woman during her life time if she conformed to the age-specific fertility rates of a given year # of women in given 5 year age group/ # of live births to that age group for all 5 year age groups. Sum those rates then multiply by 5.
Gross Reproduction Rate (GRR) Average # of daughters that would be born to a woman during her life time if she conformed to the age-specific fertility rates of a given year # of women in given 5 year age group/ # of live birth daughters to that age group for all 5 year age groups. Sum those rates then multiply by 5.
Net Reproduction Rate (NRR) Average # of daughters that would be born to a woman during her life time if she conformed to the age-specific fertility rates andmaternal mortality rates of a given year GRR - MMR
Replacement Level Fertility Level of fertility at which a cohort of women, on the average, have only enough daughter to " replace themselves in the population. NRR = 1.0 is replacement level. See NNR
Child-Woman Ratio # of children under 5 per 1,000 women ages 15-49 # children < 5/ 15> women< 49 * K
Marital Fertility Rate # live births per 1000 married women ages 15-49 in a given year # live births/# married women ages 15-49 * K
Out-of-Wedlock Birth Ratio # live births per 1,000 unmarried women (single, widowed, or divorced) ages 15-49 in a given year # live births/# unmarried women ages 15-49 * K
Abortion Ratio # abortions per 1000 live births in a given year # abortions/# live births * K
Abortion Rate # abortion per 1000 women ages 15-44 in a given year # abortions/# women 15-44 * K

Mortality
Death Rate
(Crude Death Rate)
# of deaths per 1000 population in a given year # deaths/Total Pop * K
Age-Specific Death Rates Often given separately for sex, race # deaths in group/Tot Pop of group * K
Cause-Specific Death Rates Deaths per 100,000 due to specific cause # deaths from cause/Tot Pop * K
Proportion Dying of a Specific Cause Deaths of a specific cause expressed as a percentage of all deaths # deaths in group / Total Deaths
Infant Mortality Rate # deaths to infants under one year of age per 1,000 births in a given year # deaths infants <1 year / Tot Births * K
Perinatal Mortality Rate # of fetal deaths after 28 weeks of pregnancy (late fetal deaths) plus the number of deaths to infants under 7 days of age per 1000 live births (# fetal deaths + infants deaths < 7 days)/ Tot live births * K
Postneonatal Mortality Rate # of infant deaths at 28 days to one year per 1000 live births in a given year # infant deaths >28 and less than one year/ Tot live births * K
Maternal Mortality Rate (MRR) # of women who die as a result of childbearing in a given year per 100,000 births in that year. # maternal deaths/ Tot live births * K
Life Expectancy Est. of the average number of years a person can expect to live, based on the age-specific death rates for a given year. Usually separated by sex, present age and race.  
The Life Table Used to simulate life-time mortality of a hypothetical population of 100,000 all born at the same time. Initial life expectancy (first entry in Col (4) is known. Col (1): Proportion dying in the age interval.
Col (2): # living at beginning of interval
Col (3): # dying in interval = Col (1) * (2)
Col (4): Person years lived in this and subsequent intervals = Col (2) * Col (5)
Col (5): Years of life remaining = Col (4)/Col (2)

Morbidity
Incidence Rate # of persons contracting a disease during a given time period per 100 or per 1,000 or per 100,000 population at risk # of persons developing a disease during a given time period/ Tot Pop at Risk * K
Prevalence Rate # persons having a disease at a given point in time per 1,000 population at risk # of persons with a specific disease/ Tot Pop at Risk * K
Case Rate # of reported cases of a specific disease or illness per 100,000 populatin during a given year. # of reported cases of a disease during a given year/ Tot Pop * K
Case Fatality Rate the proportion of persons contracting a disease who die from that disease # persons dying from the disease/# persons developing the disease * K

Nuptiality
Marriage Rate (Crude Marriage Rate) # of marriages per 1,000 total population in a given year # marriages/Tot Pop * K
Median age at First Marriage ½ the people marrying for the first time in a given year got married before the median age and ½ after  
Divorce Rate (Crude Divorce Rate) # of divorces per 1,000 population in a given year. Note: this is the # of divorces and not the number of people getting divorced # of divorces/ Tot Pop * K
Remarriage Rate # of remarriages per 1,000 poulation of currently divorced or widowed men or women # of remarriages/ Tot Pop of widowed and divorced women or widowed and divorced men * K

Migration
Immigration Rate # immigrants arriving at a destination per 1000 population at that destination in a given year # immigrants/ Tot Pop at destination * K
Emigration Rate # emigrants departing an area of origin per 1000 population at that area of origin in a given year # emigrants/ Tot Pop at origin * K
Net Migrations Net effect of immigration and emigration on an area's population immigrants - emigrants
Net Migration Rate Net effect of immigration and emigration on an area's population, expressed as increase or decrease per 1000 population of the area in a given year (#immigrants - #emigrants)/ Tot Pop * K

Race and Ethnicity
Race Definitions vary depending on the individual country's situation and needs.  
Ethnicity Distinguishes people on the basis of cultural characteristics such as language or national origin. Pop of a given nationality/ Tot Pop * K
Foreign Born Population Persons born outside of the borders or territories of a country Foreign born persons/ Tot Pop * K

Households and Families
Household One or more persons who occupy a single housing unit. Households consist of unrelated persons or persons related by birth, marriage or adoption. Persons living in households/Tot Households = average size (#of persons per) of household
Family Two or more persons residing together related by birth, marriage or adoption. Married couple families/Family Households * K = proportion of family households headed by married couples.
Singe-Parent Families Single-parent families have children maintained by one parent as a result of an out-of-wedlock birth, divorce, separation or death of a spouse. Single-parent families/ Tot households * K = proportion of households maintained by a single parent.

Urbanization and Distribution
UrbanDepends on nation:
Japan 50,000 > urban

US 2,500 > urban
 
Metropolitan Usually an area > 100,000 or more people with an important city at is core plus suburban and "exurban" areas that surround the city and are socially ad economically integrated with it.  
Population Density Expressed as the number of people per unit of land area. Often given in terms of arable land. Other times in terms of average number of persons per household or per room. Total Population/ Total land area
Percent Urban Population living in urban areas expressed as a percentage of the total population. # living in urban areas/Tot Pop * K

Population Change
The Balancing Equation Basic method of calculating numerical population change over time. P2 = P1 + (B - D) + (I - E) Where:
P2 = pop at later date
P1 = pop at earlier date
B = Births
D = Deaths
I = Immigration
E = Emigration
Natural Increase Surplus (or deficit) of births over deaths in a population in a given time period. NI = B - D
Rate of Natural Increase Rate a 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. This rate does not include the effects of immigration or emigration. (# birth given period of time) - (#deaths given period of time) / Total Population mid-period of time * K
 
or:
 
Birth rate - Death rate)/ 10
Growth Rate Rate at which a population is increasing (or decreasing) in a given year due to natural increase and net migration, expressed as a percentage of the base population. Never to be confuse with Birth Rate. (Births - Deaths + Net migration)/ Tot Pop * K
 
or:
 
Rate of natural increase + Net migration rate
Doubling Time Time, at current growth rate, a population would take to double in size. (See explanation and examples). Quick calculation:
70/ Growth rate (%)*
 
*growth rate % expressed as an integer
The Demographic Transition Stage I: High birth rate, high death rate = modest growth
Stage II: High birth rate, falling death rate = high growth
Stage III: Declining birth rate, relatively low death rate = slowed growth
Stage IV: Low death rate, low birth rate = very slow growth
 

 
 
 
 
 
Additional references:
 
Population: an Introduction to Concepts and Issues by John R. Weeks. A college textbook and a good introduction to population issues, including terms and definitions.
 
World Population Growth, by George E. Immerwahr. This excellent book explains population growth in clear, concise terms and contains an excellent demographic appendix.

 
 


 
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