Introduction
The monthly Index of Services (IoS) has been developed to provide a timely indicator of growth in the output of service industries, at constant prices. The monthly IoS is a key component in the development of a monthly GDP indicator. IoS shares exactly the same industry coverage as the corresponding quarterly series within GDP(O).
An IoS development programme is currently taking place to review, industry-by-industry, the data sources and methods used to estimate the monthly IoS and the quarterly gross value added of the service industries, making improvements to the methodology and incorporating more monthly data sources where possible. More information about this programme can be found in the section on Future Improvements.
A sign of the progress already made by the IoS development programme is that from the January 2007 release published on the 29 March 2007, the IoS has been reclassified from an experimental series to a mainstream National Statistic. This is in recognition that over 77 per cent (by share in the economy) of the IoS is now designated as having met National Statistics standards.
The monthly IoS is currently published for total services, five broad industry categories and 21 of the 25 2-digit SIC divisions within services. At the time of writing, 4 of the 5 broad industry categories and 13 of the 21 published divisions have been classified as National Statistics. Those broad industry categories and 2-digit SIC divisions published (with National Statistics denoted in bold) are:
Distribution
Division 50: Motor Trades
Division 51: Wholesale Trades
Division 52: Retail
Hotels and Restaurants
Division 55: Hotels and Restaurants
Transport, Storage and Communication
Division 60: Land Transport
Division 62: Air Transport
Division 63: Supporting and Auxiliary Transport Activities
Division 64: Post and Telecommunications
Business Services and Finance
Division 65
Division 70: Real Estate Activities
Division 71: Renting
Division 72: Computer and Related Activities
Division 74: Other Business Activities
Government and Other Services
Division 75: Public Administration and Defence
Division 80: Education
Division 85: Health and Social Work
Division 90: Sewage and Refuse Disposal
Division 91: Activities of Membership Organisation nec
Division 92: Recreational, Cultural and Sporting Activities
Division 93: Other Service Activities
Division 95: Private Households with Employed Persons
The documentation explains the methodology used to estimate the IoS. The main body of the documentation provides the reader with a basic understanding of how the IoS is constructed. Within this there are links to annexes that provide a more detailed explanation of some parts.
The documentation explains the Conceptual Basis of the IoS, what gross value added is and the types of indicator that are used as proxies for the movement in gross value added of the service industries. The documentation explains the stages of processing in constructing the published indices from the source data and provides a description of the Index Construction. All of the Source Data are listed, along with their periodicity and their weight within IoS. Overviews of the Time Series Methods used for forecasting, interpolation and seasonal adjustment are provided and the process for Quality Assurance of the data and applying ‘quality adjustments’ is explained. The way the IoS fits into the National Accounts framework and the process of applying GDP ‘coherence’ adjustments are also explained. The annexes provide more detailed explanations of index number construction, forecasting, interpolation, seasonal adjustment and the approach to making quality adjustments.
For each industry reviewed, a report is produced to explain the review process and the decisions taken on the most appropriate sources and methodology. These reports will be held on the National Statistics website and can be accessed via the Future Improvements section of this documentation.
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