Literal question
5. Age
In completed years i.e., age on last birthday (in two digits e.g., 02, 24, 99). Put "00" for infants younger than one year.
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Interviewer instructions
2.4.6. Column number 6 - Age
For age, you will inquire the age on the last birth day and write age in two digits (age 02 will be written for those who have completed two years, age 34 will be written who have completed thirty four years and 99 years for those who are of ninety nine age or more). Those infants who are of age less than 1 will be written as "00". In some cases the respondent may not be able to tell correct age of a few persons; then he may be helped in determining the age.
National or international events like World War II 1939-45, creation of Pakistan 1947 Quaid-e-Azam's death in 1948, Indo-Pak War in 1965 and 1971, etc. or the reference of certain local events can help in determining correct age.
The age of some persons can be determined with reference to those people whose age is known, especially when you start with youngest person. The married people know their age with reference to their marriage. They may also remember after how many years of marriage their eldest child was born and after how many years gap was there between later children. If age of one member of the household is known the correct age of other members can be determined.