1.2.1. Questions for ALL Household Members
6. and 7. Column P6 and P7: Date of birth and age
The census enumerator should devote to this part a special care, since these questions are by themselves of utmost importance, since the age variable will play a major role in the analysis of the data collected.
Principles for determining age from the correspondence tables:
Determining the age shall be done, whenever possible, from a birth certificate. If this is true that in urban areas most children will have a birth certificate, this is however not the case in rural areas. Indeed, the high rate of illiteracy is a major handicap for the functioning of vital registration in rural areas. Therefore, in these areas, the age is expressed as the number of rainy seasons seen by the person.
Furthermore, one should note that in rural areas, references are made to the lunar calendar, translated into vernacular languages.
This is why a correspondence table was established, in order to allow the precise determination of the date of birth for children less than 10 years of age, according to the Gregorian calendar. This technique is based on the knowledge by the respondent of three elements:
1. The number of rainy seasons lived by the child;
2. The name of the lunar month of the birth of the child;
3. The day of birth of the child in the lunar calendar.
Example: A respondent tells you that his or her child has lived 6 rainy seasons, that he or she was born on Ramadan 27. What is the exact date of birth of the child?
Response: Refer to the correspondence table provided in Annex 2. Read the intersection of line "sounkalo" and Column "6 rainy seasons". You will find that the date of birth lies between February 23, 1993 and March 23, 1993. To obtain the precise date, add 26 (that is 27 - 1) to February 23, which gives 49. Then Subtract 28, corresponding to the number of days in February, and one obtains 21. The child is therefore born on March 21, 1993. Then, one can calculate the age of the child, as if he or she had a birth certificate. If the date of enumeration is March 16, 1998, the child's age is therefore: 4 years and 11 months, or 59 months.
If the child is born on Ramadan 3, the precise date of birth will be obtained as 23+3-1 = 25, and the child's birth date would be February 25, 1993.
In general, if the result of the computation for days is higher than the number of days in the months, one shall subtract this number from the result to obtain the corresponding date.
If the first element of the calendar is known, and the two others are unknown, one could use, when needed, the approximate agricultural calendar (see Annex 3), for an estimation of the child's date of birth.
7. Column P7: Age
Age will be determined for the individuals who know their date of birth, as well as for those who do not have any official document, with their month and year of birth.
Ask for the age of the person, and write it in the two boxes located in Column P7. Do not forget to circle the number of the unit in which the age is expressed: 1 = Days, 2= Months, 3= Years.
Age will be determined in integer number of years for the persons aged 1 year of more, and in integer number of months for the infants (less than 1 year or less than 12 months). For example:
- A person aged 30 years and 8 months will be written:
- A person born in 1950 will be written: 1998 - 1950 = 48 years
- A baby aged 4 months and 28 days will be written.
- A new born baby aged 15 days will be written = 15 days
Please pay special attention to the writing of the age of infants (less than 1 year of age). The age of these children shall be determined in integer number of months. Use, when possible, the seasonal calendar in Annex, for which the principle of use has been described in the "Date of birth" section.
N.B. The age in integer number of years is obtained the following way:
a) By subtracting the year of birth from 1998, if the birthday date (day and month) is already passed at time of the interview.
b) By subtracting the year of birth from 1997, if the birthday date (day and month) is not yet passed at time of the interview.
Remark: Providing the date of birth does not exclude mentioning the age.
Persons who do not know their age:
It might happen that during the census operations, that you encounter persons who do not know their age. You shall then help these persons to estimate their age, using one of the following methods:
Method 1: Historical calendar
The historical calendar is a list of noticeable events (national or local), with their dates, which have a special influence on national life in general, or on the life of local communities in particular.
The determination of the age of a person using the historical calendar is done by estimating his or her age at time of one of these events, and as a consequence to estimate his or her date of birth. Then one subtracts it from the census date in order to obtain an approximate age.
For using this historical calendar, one shall proceed as such:
- One starts with a rough estimation of his or her age, by looking at the person.
- Let us assume "30 years". To obtain the departing point on the calendar, one adds 5 years to the age, that is, 30 + 5 = 35 years. Then one subtracts this number from the census year, that is: 1998 - 35 = 1963.
- One then looks in the historical calendar for events located around 1963, and one quotes the event to the person, asking: "Do you remember this event?"
a) If the answer is "yes", then one asks: how old were you at that time?
Assume that the person answers with certainty "10 years". Then this person is born around 1963 -- 10 = 1953, and his or her age is then = 1998 - 1953 = 45 years.
b) If the answer is "no", then go to another event.
Method 2: Classifying persons among themselves
Some household members do not know accurately their age, but may remember being somewhat older or younger than other household members, or in the neighborhood.
If one can determine with precision the age of one or several of these persons, then one could deduce an estimation or the age of the person who does not know his or her age.