QUALITY OF AGE DATA IN THE NIGERIA DEMOGRAPHIC AND HEALTH SURVEYS 1990-2013

Abstract

Information collected about age is an important variable in a survey and census because of its usefulness in providing further demographic analyses and estimations, such as estimation of fertility and mortality, migration estimation, population estimation and estimation of demographic parameters and model. Age is one of the key demographic variables and it is the primary basis of demographic classification in censuses, vital statistics and surveys. Age data are also very essential in calculating the basic measure relating to the components of change (fertility, mortality and migration), as well as in the study of population projections and nuptialitics. Much of the demographic information in use is expressed in terms of age at which something happens. Therefore due to the frequent use of NDHS datasets in carrying out research in Nigeria, quality of age data in the NDHS 1990-2013 were examined in the study. Ages are commonly rounded with terminal digit 0 and 5, this has resulted in digit preference. The mechanisms for data collection put in place in Nigeria is worse. Inaccurate data reporting in Nigeria has affected most of the research conducted in Nigeria. Surveys no matter how it is being obtained are subject to errors. These errors are troublesome as they occur frequently and their presence also introduce subsequent errors. The study is examining the quality of age data in the NDHS 1990-2013. The study evaluated the accuracy of age data reported from the NDHS 1990-2013; examined the level of age misreporting among males and females in the surveys; determined age preference and/or avoidance among the males and females in the survey; and finally assessed the pattern of age deviations of the reported from the stable age distributions. The study was a cross-sectional and the data were obtained from the NDHS age datasets for the households. The age data reported were grouped into 5-years range and the UN Age-Sex Accuracy Index were used to check for irregularities in age data. Also the ages were cumulated into 5-year range and the Coale-Demeny Model life Table for estimating deviations in age data were used to correct such erroneous age data. The results of the study revealed that across all the surveys, quality of age data were inaccurate; preference for terminal digits "0" and "5" were very much pronounced among males and females; revealed that the patterns of preferences were the same among males and females; found higher degree of deviations of the reported from the stable age distributions. The quality of age data in the NDHS 1990-2013 were very inaccurate and no significant improvement were observed between the surveys. This may result in wrong estimations, wrong projections, wrong planning and developments in entirety in Nigeria may be retarded. Hence, it is recommended that the Coale-Demeny Model Life Table for the "West" is considered the best method to correct such erroneous age mis-statement, because of its effectiveness in estimating the patterns of deviations in age data especially for country like Nigeria.