presented by GAMBO, LOUIS LAWAI National Bureau of Statistics Abuja, Nigeria.

1. 4th AFRICAN SYMPOSIUM ON STATISTICAL DEVELOPMENT IN AFRICA, LUANDA,ANGOLA, 09-13 FEB 2009.CODING AND EDITING OF CENSUS DATA NIGERIAN EXPERIENCE presented by GAMBO, LOUIS LAWAI National Bureau of Statistics Abuja, Nigeria.

2. OUTLINE OF PRESENTATION • INTRODUCTION • OBJECTIVES • COVERAGE • METHODOLOGY • CODING AND EDITING

3. INTRODUCTION • Nigeria has witnessed 12 censuses from 1866, 1871, 1896, 1901, 1911, 1921,1952/53, 1962, 1963, 1973, 1991 and the last was in 2006. • These series of censuses have led the country into lots of experiences • Which include data collection, processing, coding, editing, archiving, dissemination etc. • The evidence-based knowledge from the series of censuses made coding and editing in the last Population and Housing census 2006 a huge success

4. OBJECTIVES • Why Coding? • Grouping of activities into adopted classification with 3 space provided in questionnaire as required by ILO and NBS • To capture responses on description of activity • To capture major occupations and also the minor ones in each group

5. COVERAGE • Coding procedures were applied to all activities or occupational groups • To all major and minor groups of activities or occupations • To all parts and sections of activities or occupations in the questionaires.

6. METHODOLOGY 1/5 • Before editing and coding commenced different cadres of staff were trained. • Training of the trainers (TOT) at the headquarters. • Training of supervisors at 7 centers (zonal headquarters). • Training of enumerators at the Local Government Areas (774). • The skills acquired were tested in the pilot Census in 7 states. • Corrections, observations were made against the real Census 2006. • Manuals and other tools were finalized in readiness for the real Census.

7. METHODOLOGY2 /5 • Experience will be restricted to geo-coding and occupational coding due to limited time. • Geo-coding was applied to: - Household types eg Regular household 1, Institutional households 2, Homeless household 3, etc. - EAs were coded. - Local Government Areas were coded. States were coded (alphabetically). • Political stability made: - State and Local Government creation minimal. -Boundary adjustments became stable. -EA demarcation was carried out with ease. -However Delta Region was a conflict zone (managed by the indigenes).

8. METHODOLOGY 1/5 • There were nine (9) major groups of occupations (activities) coded thus 100, 200…..900 • The major occupations (activities) included: • Professional, Technical and Related workers; • Administrative and Managerial workers; • Office and Administrative support workers; • Sales and Related workers; • Service workers;

9. METHODOLOGY 2/5 • Installations, Maintenance and Repair workers • Agricultural, Animal Husbandry and Forestry workers, Fishermen and Hunters • Production, Construction and Extraction workers • Transportation and Material Moving workers

10. METHODOLOGY 3/5 • Each major group had a detailed member of minor occupations (or activities) • For example, Professional, Technical and Related workers’ group had minor groups ranging from 101 to 179 • While 199 was reserved for occupations related to the major group but had not been adequately described or covered by existing minor groups; or had been newly discovered but unclassified in the coding exercise • The newly discovered was coded 199 as related to the major group in this example.

11. METHODOLOGY 4/5 • There were eight (8) categories of personnel involved in the coding exercise viz: • Project Coordinator • Coordinated activities of coding officers in all the 7 Data Processing Centres (DPCs) • Data Processing Managers • Technical heads of DPCs that worked in collaboration with the DD (IT) and Coding Officers • Coding Officers • Administrative heads of the coding at the DPC

12. METHODOLOGY 5/5 • Assistant Coding Officers • 2 in each DPC; assisted the Coding Officers to effectively oversee the coding exercise • Server Officers/Administrators • Timely extraction of images for storage Area network (SAN) and distributed same to workstations for coding • Coding Supervisors • Responsible for the technical supervision of the workstation assigned to them • Coding Clerks • Responsible for assigning appropriate codes to all occupations recorded in the questionnaires (NPC 01 and NPC 02)

13. CODING 1/4 • In Census studies there are two (2) types of questionnaires • Pre-coded questionnaires • Usual questionnaires that have had codes assigned to the questions already • Post-coded questionnaires • Usual are questionnaires whose codes are determined after the field work had been done • The Population and Housing Census questionnaires were pre-coded, so these was little left to do as regards post-coding

14. CODING 2/4 • The duty of the enumerators was to interview a household (HH) and enter the codes according to the questions • In most cases all the questionnaires were pre-coded; the enumerators only entered the required codes appropriately. • The codes were either entered inside the boxes by printing the numbers or otherwise circled the option • It was expected that no questions should be left blank except where there is a skip instruction • Completed questionnaires were returned to data processing centres

15. CODING 3/4 • At the processing centre editors first of all cross check whether the questions were properly coded • The questionnaires were usually coded using the interviewer’s manual where applicable. • Where editors could not correct the questionnaires that were not properly filled, such questionnaires were returned to the enumerators for proper completion.

16. CODING 4/4 • At end of the coding exercise the coded questionnaires were batched according to enumeration areas and sent to the manual editors • Manual editors were the team that thoroughly checked the questionnaires before data entry and scanning began. • Some questionnaires(digital) were scanned while the analog ones had data entry

17. EDITING 1/3 • Coding and Editing cannot be separated because the former (coding) assigns numbers to described occupations that are seen to be similar, the latter ensured that the assigning exercise was done correctly and according to classified standards.

18. EDITING 2/3 • Editing arose due to insufficient briefing on the grouping of activities or occupations that were not properly described • The Minor groups that were not on the classified list, but were coded while the exercise was on needed to be scrutinized to ensure the correct coding had been done • To ensure coding that was carried out in the absence of Assistant Coding Officer was understood by the Coding Clerks

19. EDITING 3/3 • Editing covered all sections and stages of coding • To ensure uniformity and consistency in all the Data Processing Centers (DPC) • To ensure that these errors were avoided • Omission error • Double error • Inconsistency error • Wrong entry error

20. EDITING METHODOLOGY

21. End of Presentation Thank you