Sum of age-specific-fertility-rates over all ages (from 15 to 44 or 49) yields total fertility rate (TFR). It is interpreted as the average number of children ever born among women in the age group 15-44 (sometimes 15-49). This is the birth performance of a group of women who all start reproductive life (age 15) together and experience schedule of ASFRs as existing in a particular year. It is, however, a technical concept. It does not show actual fertility of any real group of population. Yet, it is widely used as a measure of fertility as it does not depend on age distribution of population. If ASFRs are computed for five year age groups then the sum of them is multiplied by five.

As in case of fertility, mortality rates are also computed separately for different ages or age groups. Thus age-specific-death-rates (ASDRs) are defined as ratio of number of deaths in a year aged x to number of persons aged x. As changes in mortality from one age to another are not so sudden ASDRs are computed for five year age groups.

The most commonly used measure of mortality is life expectancy which refers to the time in years for which a new born child is expected to live. Life expectancy at birth is calculated from age-specific-death-rates (ASDRs). Since there are gender differences in ASDRs, life expectancy is calculated separately for males and females.

Number of infant deaths, i.e., deaths of children in age group 0-1 year per thousand births is called infant mortality rate (IMR). Likewise one can also define child mortality rate (CMR) for children aged 0-5 years. IMR is considered to be an indicator of both development and health services.

Migration rate can be defined on the pattern of crude birth rate and crude death rate. However, in countries where migration records are not kept and migration data are collected from surveys or censuses some other measures are employed. These measures and measures of social mobility are beyond the scope of this course.

For calculating the above measures one needs data on size of population, age-and-sex composition of population and births and deaths by age.

The sources of data are: population census; vital registration system; sample registration system; national and regional surveys; administrative data collected from routine records of various government departments.

These sources of data will be discussed in Module 3 on "methods".