Some Basic Concepts of Demography:
1. Live Birth: Live birth is the complete expulsion or extraction from its mother. Live birth is the beginning of life and influences population. Live birth is very important both in growth of population & social life.
2. Still Birth: When one thinks of birth in demography one includes in it both live birth & still birth. Live birth is of course somewhat simpler in counting because in it are counted all those children who did not come out of the womb of the mother but the woman remained pregnant for 28 weeks.
3. Family Size: Though commonly from family size, we mean total number of persons of a family, yet in demography it does not mean so. In demography, it means number of children a woman or couple has at a point of time. The complete family size indicates the total number of children born by a woman up to the end of her reproductive period.
4. Child Death: Usually due to social or other causes there are many deaths in many countries within a period of one year of the birth of the child. In some cases, whereas newly born baby dies, in some both the baby as well as mother dies. This increases death rates as well.
Deaths which occur within a period of 4 months from the birth of a child are known as Neonatal period of deaths. The deaths which takes place between a period of 4-12 months are known as Post Neonatal Period of deaths.
5. Sterility: A man or woman or couple who has not given birth to child is called sterile. It is used both in connection with individuals or groups consisting either men or women or both. But usually sterility measures are computed only for women.
6. Parity: In demography women are classified according to the number of children born alive to them. As for example, first parity women are those who have given birth to one child, second parity women are those who have given birth to two children & so on.
7. Adulthood: Adulthood means that it is at this stage that boy or girl becomes capable to produce children.
8. Reproductive span: It indicates child bearing period of a woman. Only women can conceive & give birth to children & that too within a limited period & certain age limits.
9. Fecundity: Fecundity is that stage in a life of girl by which she becomes capable of becoming mother, no matter whether she actually becomes or not. If she is capable of giving birth to a child she is called fecund.
10. Fertility: Fertility is tha standard of measuring the capacity of the women to produce children. According to Thomson & Lewis, “the born fertility is generally used to indicate the actual reproductive performance of a women or a group of women. The crude birth rate is only one measure of fertility."
Thus it is obvious that a fecund woman may not be fertile but a fertile woman must be fecund because if she is not then fertility has no meaning.
11. Cohort: In demography the children who are born in one year are called cohort.
12. Relative Number: Relative numbers are needed only when comparison is desirable. Both the ratios & rates are relative figures & expresses a relation between two or more numbers.
13. Ratio: Ratio expresses the size of one to another. As for example male female ratio in a country or a region etc.
14. Rates: Like another ratios, a rate is also computed & that help in expressing what has happened in terms of a certain unit of time. Two most commonly used rates in Demographic studies are Birth & Death Rates.
15. Birth Rates: The procedure for calculating birth rate is by finding out total number of births in a given area during a given year and by dividing that by total number of people living in an area at the mid-point of that year and multiplying that by 1000.
16. Death Rate: Death rate is also computed by the similar way as the birth rate.
17. Crude Rate: Both birth rate & death rate are however called CRUDE Rate. Because, these (birth rate & death rate) use total population as a base number rather than parts of the population.
Usually midyear population is used because it is probably the figure which is both nearest to the average population for the year a readily obtainable.
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