This briefing note describes the approach used for the secondary analysis of quantitative data in the Commission’s report Reducing the cost of assessments and reviews: An adult social care briefing. The analysis underpinning this report is based on a calculation of the unit costs of conducting assessments and reviews across a sample of councils returning reliable data between 2005/06 and 2010/11. The sample was chosen to exclude councils with changes in data that were outside the range we would expect by chance. The variable of interest is cost per assessment and review, defined as spending on assessment and care management (ACM) in any year divided by the number of assessments completed and the number of reviews carried out during the year. Spending figures are deflated using the GDP deflator to a 2010/11 price base to allow comparison over time. This briefing note contains information about the data sources used in the analysis, the selection of councils in the analysis, the approach used to develop the levelling exercise in the analytical model, and steps taken to mitigate the risks involved. The appendices contain detail about the indicators used to identify variation between councils, and the financial impact of the levelling at a council level.