Age heaping and numeracy: looking behind the curtain

Abstract Age-heaping-based numeracy indicators have served as valuable tools to derive basic human capital estimates, especially for periods where other indicators are unavailable. However, the accuracy of individual age statements usually remains unknown, and due to the lack of precise information it can only be assumed that excessive occurrence of multiples of five in age distributions reflects inferior numerical skills. This article addresses this lacuna by identifying 162 individuals in two independent data sources: self-reported age statements and independently kept records which are based on family heritage books and church registers. This method makes it possible to identify individual misreporting and the degree of accuracy of each individual. Findings show that not everyone who reported a multiple of five was reporting an incorrect age, nor was it the case that everyone who reported an age that was not a multiple of five was reporting an accurate age. The empirical analysis shows that the commonly used binary numeracy indicator is correlated with the observed degree of accuracy in age statements, and that a more sophisticated occupational background reduces this inaccuracy. These results tentatively suggest that the commonly used binary indicator measuring age heaping is a valuable proxy for numerical skills and occupational background in a population.