Age structure. The distribution of a population according to age, usually by 5-year age groups.
Age-specific fertility rate. The number of births during a year to women in a particular age group, usually per 1,000 women in a 5-year age group at midyear.
Aging. An increase in the proportion of the population in the older ages. May also be measured as an increase in the median age of the population.
AIDS. Acquired immune deficiency syndrome.
ART. Anti-retroviral therapy.
Births. The number of live births occurring during a given calendar year.
Birth rate. The average annual number of births during a year per 1,000 population at midyear. Also known as the crude birth rate.
Cohort. A group of individuals born in the same calendar year or group of years. Also referred to as a birth cohort.
Components of change (of population). Fertility, mortality, and migration.
Crude birth rate. The average annual number of births during a year per 1,000 population at midyear.
Crude death rate. The average annual number of deaths during a year per 1,000 population at midyear.
Deaths. The number of deaths occurring during a given calendar year.
Death rate. The average annual number of deaths during a year per 1,000 population at midyear. Also known as the crude death rate.
Dependency ratios. A population’s dependency ratio, also known as the age dependency ratio and the total dependency ratio, is the combined child population (people under age 15) and elderly population (people ages 65 and above) per 100 people ages 15-64 (people “of labor force age”). The youth dependency ratio is the number of people under age 15 per 100 people ages 15-64. The elderly, or old age, dependency ratio is the number of people 65 and over per 100 people 15-64. Dependency ratios are also referred to as support ratios.
Dependent age groups. People under age 15 and people 65 years of age or older.
Development category. The classification of regions into “less developed” and “more developed” according to their general level of economic development. Countries are classified according to the grouping used by the United Nations. See references to these terms in the Glossary for details.
Growth rate. The average annual percent change in the population, resulting from a surplus (or deficit) of births over deaths and the balance of migrants entering and leaving a country. The rate may be positive or negative. Also known as population growth rate or average annual rate of growth.
HIV. Human immunodeficiency virus. The virus that causes AIDS.
Infant mortality rate. The number of deaths of infants under 1 year of age from a cohort of 1,000 live births. Denoted 1q0 or IMR, it is the probability of dying between birth and exact age 1.
Less developed countries. The “less developed” countries include all of Africa, all of Asia except Japan, the Transcaucasian and Central Asian republics, all of Latin America and the Caribbean, and all of Oceania except Australia and New Zealand. This category matches the “less developed country” classification employed by the United Nations. “Less developed” countries are sometimes referred to as “developing” countries.
Life expectancy at birth. The average number of years a group of people born in the same year can be expected to live if mortality at each age remains constant in the future.
Life table. A statistical table that follows a hypothetical cohort of 100,000 people born at the same time as they progress through successive ages, with the cohort reduced from one age to the next according to a set of death rates by age until all people eventually die.
Median age. The midpoint age that separates the younger half of a population from the older half.
Midyear population. The population estimate for July 1 of the given year.
Modern methods of contraception. Condoms, IUD’s, pills, vaginal methods (spermicides, diaphragms, or caps), injectables, and voluntary sterilization of a woman or her partner.
More developed countries. The “more developed” countries and areas include all of North America and Europe plus Japan, Australia, and New Zealand. This category matches the “more developed” classification employed by the United Nations.
Natural increase. The difference between the number of births and the number of deaths.
Net migration rate. The difference between the number of migrants entering and those leaving a country in a year, per 1,000 midyear population. May also be expressed in percent. A positive figure is known as a net immigration rate and a negative figure as a net emigration rate.
Net number of migrants. The difference between the number of migrants entering and those leaving a country in a year. A positive figure is known as net immigration and a negative figure as net emigration.
Pandemic. A global epidemic.
Population pyramid. A graphical representation of the age and sex distribution of a population. Numbers or proportions of males and females in each age group are plotted as horizontal bars with the males on the left and females on the right. Pyramids may be constructed to show single years of age or, as with the IDB pyramids, 5-year age groups.
Rate of natural increase. The difference between the crude birth rate and the crude death rate, but usually expressed as a percent rather than per 1,000 population.
Total fertility rate. The average number of children that would be born per woman if all women lived to the end of their childbearing years and bore children according to a given set of age-specific fertility rates.
Traditional methods of contraception. Periodic abstinence, rhythm, withdrawal, douche, prolonged breastfeeding, and folk methods. Also known as natural methods.
UNAIDS. The United Nations Joint Programme on HIV/AIDS.
Under-5 mortality. Number of deaths of children under 5 years of age from a cohort of 1,000 live births. Denoted 5q0, it is the probability of dying between birth and exact age 5.
Vital events. Births and deaths.
Vital rates. Birth rates and death rates.
