TDB Advisory was asked by the Royal Commission of Inquiry into Abuse in Care to undertake an independent peer review of a draft report by MartinJenkins. The MartinJenkins report was tasked with estimating the prevalence of abuse in State care and faith-based organisations between 1950 and 2019. A difficult challenge given the limited data. Our peer review highlights the issues that arise from extrapolation and interpolation of data and identifies methodologies available when there is insufficient hard data to make accurate estimates.