The IOS is a National Statistics survey designed to measure changes in quarterly output for the Service Sector. The sampling frame used is Inter-departmental Business Register (IDBR). A stratified sampling technique known as the Neyman Allocation is used. Each stratum is indexed currently using 2010 = 100 as the base year. The overall Index of Services is calculated by weighting together industry level indices that describe the activity of an industry sector using the Standard Industrial Classification (SIC). Weights are based on the relative share of regional GVA on an annual basis.
Quality Assurance of final estimates for the IOS had identified the need for additional checks relating to the introduction and linking of a new, boosted sample which has been collected since Q1 2014.