What is the Nature of Age Data in Population Studies?

The United Nation has defined age as “the estimated or calculated interval of time between the date of birth and the date of census, expressed in completed solar years.

It has also recommended that information on age should be collected in the census by asking the date of birth of the individual (day, month and year) or by asking a direct question to obtain information on the age at the last birthday, or by asking both these questions together.

Though the question on the date of birth obviously yields more accurate information of age, it is not always possible to obtain date of birth from a population in which the majority is either illiterate or semi-literate.

In such a situation, information on age is collected by asking about “the age completed on the last birthday.”

Though it is easy enough to ask questions on age, it is extremely difficult to obtain correct information about age when people are illiterate or semi-literate and are ignorant about their own age.

In India, it is not uncommon for enumerators or investigators in a census or demographic survey being told, “I do not know my age. May be I am 30 or 35 years old. Why don’t you decide how old I am?”

The practice of registering births is not yet widely followed in India and therefore, birth certificates are not available with the Indian people.

There is a great deal of apathy on this matter of correct age, because Indians generally do not have to face situations where they have to produce proof of age.

The Indian age data, therefore, show concentration of population at a certain age, for Indians prefer to report their age in numbers ending with 0 or 5. Errors in age reporting also creep in because of carelessness in reckoning age, misunderstanding of the question or deliberate misstatement.

As the age data maybe defective because of several reasons, demographers first evaluate them to determine the nature and magnitude of errors and then make the necessary adjustments before using such data for demographic analysis.

One illustration will suffice to indicate the need for such evaluation and adjustment. According to the 1971 Census age data, it was found that there were 10,548,600, males of age 10, while the figures for males of 9 and 11 were 5,970,600 and 4,666,600 respectively. This type of data clearly indicates a preference for the digit 0, so that even those of 9 and 11 were reported as being 10 years old.