Friday, April 13, 2012


 Ratio measures change in “X” per unit change in”y”.
Ratio = x/y
There are different types of ratio:
i)                    When we have numerator and denominator belongs to the same population.
ii)                   When we have numerator and denominator belongs to the different population (universe). We call the ratio as proportion (specific name of ratio).
                                Proportion= x/x+y
Proportion tends is equal to zero if x=0 and proportion is equal to 1 if y=0.
Ratio indicates the relative magnitude of a numerator and denominator.

Sex ratio is defined as the male population and female population presenting in percentages. As:

R= Male/Female  * 100
Sex ratio means male per 100 female. We can calculate different types of sex ratio.
Sex ratio of birth:
Number of males’ birth per 100 female births. Ratio if less than 100 means more female than male birth. If ratio=100 same number of male and female birth. If the ratio is greater than 100 means more males than females. In human population there is more male birth then female birth with ratio generally between 104 and 107.

Demographers define some age group and gave different name.
i)                    ADULT: Zero years, for purpose of classification all babies who have not reached their first birth date.
ii)                   CHILD: All those children who have not reach their fifth birth date (0-4) years.
iii)                 YOUTH: All those children who have not reach their 15 birthday (5-14) years.
iv)                 YOUNG: Adults and economically active working(15-60)
v)                  OLD AGE OR AGED: Age includes from 60+. If proportion of old age population start increasing then this type of population is called ageing population.

Dependency ratio is observed as;

It is not calculated for entire world but for small segment:

It is defined as the ratio between populations in a segment of territory to the total population of the country. For example;

It is the ratio between total populations to the total area to which the population belongs, for example:
It shows how densely an area is populated. A low value indicates sparsely populated area.

Rate measures the frequency with which an event occurs in a define population during a given length of time. Rates are special cases of a ratio. Rates are associated with population changes. Numerator counts of events that occur during a period. Denominator is a mid point population or person years or other person time unit of exposure for the same period at the numerator.

ASFR through gives an indication of fertility behavior in a very logical manner, however, it requires a grasp of about 7 values. Hence to abbreviate and to arrive at a one single index ASFR are summed and multiplied by size of age groups of mother (k) to yield Total Fertility Rate (TFR).

A mother (female) is going to be replaced by female in future, therefore, as an index of replacement we must calculate an index taking female birth only. Hence multiplying the TFR by the ratio of female birth with total births, yielding a new index known as Gross Reproduction Rate (GRR)

Where F: ratio of female births.

However all female born will not survive to reach the age of their mothers, hence a further refinement in GRR is made by multiplying it by the proportion of survival si, the resultant is known as Net Reproduction Rate (NRR).

Where si: survival proportion of female and birth to age of their mothers. This can be found from lx column of life table si = li/l0.
Generally TFR > GRR > NRR and the ratio between them is around 50%.


  1. Your blog is very informative and I am here with the simple and exact definition of ratios and proportion,The ratio is said to be a comparison between two similar quantities that is obtained by dividing one quantity with the other and they are represented by : symbol and proportion is a statement which shows the equality of two ratios.