Carving Up a Country

For some time now I have been involved as an advisor on GIS and Mapping in preparation of the Population and Housing Census of one of the biggest, in terms of population, African countries: Nigeria. Accurate, reliable, detailed and up-to-date data on where and how a country’s population lives, its age structure, sex ratio, internal migration, condition of health, level of employment, and level of literacy is essential for many purposes. Such data is fundamental and key for the planning and construction of roads, railways, bridges, ports and so on. It is also vital for determining location, type and size of schools, hospitals and factories, and future numbers of teachers and medical doctors. In short, census data is invaluable for planning and carrying out any economic, political or socio-cultural activity.

De facto but Dear
The methods used for carrying out a Population and Housing Census can be divided into three main categories:

• group assembly method
  
• self response method
  
• direct interview/canvasser method.

In the group assembly method, heads of households are requested to come together at a certain venue, where they are asked to submit to authorised persons pre-specified information on members of their household. In the self-response method questionnaires are posted to persons or households who are expected to fill them in and submit them to a nearby census office. Both methods are time-efficient and require no expensive resources. But each has major defects. The group assembly results in only limited information. The self-response method requires the filling in of written questions, which requires a basic level of literacy among the whole of the population. What is more, both methods face the problem of how to verify the information provided. The direct interview/canvasser method is a de facto method whereby every individual physically present in the country is interviewed face to face. This is the most reliable, but also the most expensive, method because it requires that for a period of at least two weeks enumerators must be appointed at the ratio of one to every two hundred of the population.

Biggest Peace-time Operation
The Population and Housing Census of Nigeria is a de facto method. The census is for the greater part financed from donor money to which the European Community contributes a very substantial part: over one hundred million Euro. Although in the mind of the general public a census is no more than counting people - and what’s so difficult about that? - anyone ever involved in census-taking knows what a huge and comprehensive operation it is. Indeed, it is said to be the biggest of peacetime operations in terms of planning, funding, logistics and execution, affecting as it does the entire population living within the territory.

Enumeration Area
The census period in Nigeria will cover five days in the early spring of 2006. During that period nearly one million functionaries will be on the move from one building to another, from one household to another, and between one individual in the country and another. They will interview every individual present in the country, whether of Nigerian origin or not. Four-page booklet and B2 pencil in hands, they will collect data on age, sex, occupation, educational level, employment status, marital status, school status, and so on. All these functionaries have to be trained, accommodated, transported and paid by the end of the census period. In addition, many pre-census activities are required in order to divide the landmass of this 923,768km2 country into small units: Enumeration Areas. The number of people living within an enumeration area should be fairly small, so that a team of two enumerators is able to interview every individual present within the unit during the five days of the census period. The carving up of the country into enumeration areas is done with the help of surveying methods, including the use of very high-resolution satellite images, after which the measurements are transferred onto maps. It is essential that enumeration-area maps cover every corner of the country so that no gaps occur between the areas; nor should they overlap. Because the crux of establishing such a rigorous sampling framework is that no individual is left out of the enumeration, and that no individual is enumerated more than once. The above should, I think, clearly demonstrate that in terms of logistics and number of people involved only a war effort requires greater participation on the part of the entire population.

Acceptability and Credibility
A successful census requires that the data collected and statistics derived from the data are trustworthy. The term ‘trustworthy’ here implies that on the one hand data and statistics are reliable and accurate, and on the other they are acceptable to national and international stakeholders. For example, before committing themselves to any country, overseas investors are likely first to ensure that there is no defect in the socio-economic and demographic figures provided. The same will be true for international donors. A first requirement of trustworthiness is that all processes involved are transparent and all methodologies clearly defined and scientifically sound. The recruitment of enumerators and purchase of equipment and materials should also go according to transparent procedures. Any lack of clarity in methodology, recruitment or procurement processes will affect the ultimate acceptability and credibility of the census.