Age heaping among adults in Nigeria: evidence from the Nigeria Demographic and Health Surveys 2003-2013.

Age, as a variable, represents a critical basis for demographic classification; thus, its misrepresentations or misreporting alter the accuracy of demographic estimates. This paper examines the extent and pattern of age heaping in the age data for adults, collected in the Nigerian Demographic Health Survey (NDHS). The study used the NDHS data for 2003, 2008, and 2013 to compute a Whipple's and Meyers' blended index for each survey year, by gender, geopolitical zones, states and place of residence. The analysis shows that age heaping was higher than the acceptable levels in all three data sets. The Whipple's index puts the rate of age heaping in the 2003 dataset at 271.3, whilst the rates declined slightly in the 2008 and 2013 datasets to reach 204.2 and 202.5 respectively. Similarly, the Myers' blended index portrayed that age heaping in the 2003 data was highest at 47.0 while the subsequent years were lower at 38.60 and 38.66, respectively. Digits ending in 0 and 5 were mostly reported in all three surveys and higher rates of age heaping were observed among males, the uneducated and rural dwellers. Age heaping was prominent in all three surveys, thus affecting the data quality gathered at these surveys. Thus, future studies should assess the extent to which age misreporting could bias the estimate of fertility rate.