Demography is the statistical description and analysis of human population. It refers to ascertaining the numbers and distribution of people, changes in the numbers and distribution of people over time, age and sex composition, birth and death rates among various quantities of populations.
Study of population seeks to discover the causes and consequences of population changes. The changes in population take place primarily due to changes in births, deaths and migration, which are referred to as the three components of population change. As an interplay of these three components one looks at the number of total persons which is usually referred to as size; the characteristics of population, called composition; and where are these people located, labeled as distribution of population. Prior to the discussion of the significance of the study of population it seems pertinent to explain some of the basic concepts likely to be used in this discourse.
Crude Birth Rate: The number of live births per year per thousand of the population. Total births in a specific year
------------------------------ X 1000 Total population in that year
The CBR is “crude” because (1) it does not take into account, which people in the population were actually at risk of having births, and (2) it ignores the age structure of the population.
Crude birth rates are very general statistics that are useful for making overall comparisons between different groups, societies and regions.
Fertility: The number of live-born children the average woman has. It may be called child women ratio.
Total No. of children aged 0-4 in year X
Total No. of women aged 15-49 in year X
A fertility rate is usually calculated as the average number of births per thousand women of childbearing age (15-49 years).
Total births in year X ------- X 1000 Total women aged 15-49
Fecundity: The potential number of children a normal woman is biologically capable of bearing. It is physically possible for a normal woman to bear a child every year during part of her life when she is capable of conception. While there may be families in which a woman bears twenty or more children, fertility rate are always much lower than fecundity rates because social and cultural factors limit breeding.
Death Rate: The number of deaths per thousand of the population per year.
Total death in a specific year
1000 Total population in that year
Crude death rates are also called as mortality rates.
Mortality: The number of deaths in a population.
Infant Mortality Rate: The number of babies per thousand live births in any year who die before reaching the age of one year.
Life Expectancy: The number of years an average person can expect to live. Life expectancy has increased in most societies in the world in the past century.
Life Span: The maximum number of years that an individual could live.
Migration: The Permanent movement of persons over a significant distance.
International migration: Migrant crosses the boundary between one country and another. Emigrant: When persons leave their country.
Immigrant: When persons arrive in another country.
Internal migration: Migration within a country.
The simultaneous recording of demographic data by government, at a particular time, pertaining to all persons who live in a particular territory. It usually takes place after every 10 years.
Vital Statistics: Registration of a person's birth, changes in civil status throughout his/her lifetime, and his/her death.