The second source includes children whose households were erroneously identified as having no children in the relevant age category, which appears to be most likely to affect children under three with no older siblings in the household. Guio et al (2012, p.17) dropped children aged one or two erroneously labelled as 'non-applicable' from their calculations. It is crucial that in the next round of collection of child-specific indicators, the prevalence of either type of error is minimised.