Defining and Identifying Only Children: a research note on the concept and measurement illustrated with UK survey data

Despite increasing interest in the circumstances and outcomes of only children in the demographic literature, the conceptualisation of this group has received limited scholarly attention. This Research Note argues for greater engagement by demographers and social scientists in the conceptualisation and identification of only children by addressing the following three aims. First, we outline different potential definitions of only children, presenting a framework to guide researchers’ decisions, and evaluate whether only children can reliably be identified using the British birth cohort studies. Second, we show that the prevalence estimates are contingent on the timing of measurement in childhood, indicating the need for caution when deriving only child status from cross-sectional household grid data. Third, we demonstrate that both the size and the characteristics of the only child group may differ across definitions, highlighting that the accurate operationalisation of some definitions is particularly restricted by survey design tending to prioritise mothers for data collection about children and families. We argue that researchers interested in the outcomes of only children need to consider the choice of the most appropriate measure for a given research question and, given that many datasets limit how accurately any indicator of only children can capture the chosen definition, reflect on how the operationalisation of their measure may affect the results observed.