3 To analyse total central government spending on procurement, we used data available from the Cabinet Office spend analysis tool, and our previous report Improving government procurement. All numbers were expressed in 2015-16 prices.
4 We cross-checked data on frameworks and transactions supplied to us by CCS with information available on the CCS website. We assessed start and end dates and extensions against the information provided by CCS.
5 We validated a sample of 2015-16 savings claimed by CCS:
• We reconciled savings totals reported by CCS with underlying lists of individual savings.
• We selected a sample of 30 claimed savings with a combined value of £175 million. Our sample was selected to take in savings that we considered to be high value and high risk, and other savings.
• We reviewed the methodologies and calculations behind each of the sampled savings. This was informed by interviews with the CCS staff responsible for developing the methodologies and recording savings.
• We formed an assessment of whether claimed savings met criteria for accurate public reporting of savings as set out in our 2013 report, Improving government procurement.
6 We examined CCS's use of data. We held interviews with CCS staff responsible for data, and gained first-hand experience of using the Cabinet Office's spend analysis tool.