Literal question
5. Age ____
Write the age in full years. For children younger than one year, write the months as 0/12, 1/12, 2/12, 11/12, etc.
Interviewer instructions
Age
Column No. 5 - How old did you become on your last birthday? In this column the exact age of a person in completed years at the last birthday should be registered. The age of children less than one year should be written down in twelve parts of the year, so: A child two months old will be written down 2/12; one of four months 4/12 and one of fifteen days that is less than a month 0/12.
Fractions of years or months in the age of persons should not be written down when they are older than one year. If they are five years a half years old they will be written down only as 5. Fractions and months are used only for those younger than one year (zero years).
If a person says that they do not know their age, they should find out by the approximate date of their birth with the help of known facts.
[p. 17]
If this is not possible, the age that they think they are should be written down. In no case should this information be left blank.
If the age that a person says to be ends in zero (0) or in five (5), it should be asked if this age is exact, with the purpose of eliminating the tendency to give round numbers.