Data Sources and Methodology
For each industry an index is created representing the volume of Gross Value Added (GVA) created by that industry over time.
Direct measures of value added are seldom available on a quarterly basis or on suitable timescales, so proxy indicators for output are used in their place. Example indicators include: deflated turnover; deflated production; the volume of a good or service sold or produced; and, for the public sector, a number of direct measures of output (e.g. number of pupils adjusted by attendence and attainment) and for some public services, employee numbers.
These data come from a range of sources including monthly and quarterly turnover inquiries carried out by the Office for National Statistics; published data sources (e.g. on employment levels or activity levels in certain industries); and data received directly from companies and other organisations.
A complete list of the data sources used to create output indices for each economic sector is available at the following link:
GDP Weights, Data Sources and Deflators
The index for each industry represents the volume of GVA created by that industry compared to the 'base' year (currently 2007). Figures are deflated to remove the effect of price changes over time to produce an estimate of real terms (or constant price) growth in that industry. The figures are seasonally adjusted to remove the effects of regular, calendar based cycles in certain industries.
The GVA indices for individual economic sectors are then aggregated to form an overall index of GVA (or GDP at basic prices) for Scotland. Since 2004 this aggregation has been performed using annual chainlinking - a method of annually weighted and chained estimates of volume measures - following best practice recommended by the United Nations System of National Accounts (SNA 1993).
Following publication of Input-Output (IO) analysis for Scotland for 1998-2007 in October 2010, weights for economic sectors have been updated from 2004 to 2005, 2006 and 2007, and minor changes made to weights from 1998 to 2004. Since the implementation of the latest weights, Scottish GDP estimates from 1998 to 2007 have been benchmarked to the Input-Output data, reflecting the fact that IO analysis provides the most complete and accurate measurement of GDP for those years.
Further information on benchmarking and the methodology for Scottish economic statistics is available in the Scottish National Accounts Project methodology guide.
Industry Classification
The quarterly GDP estimate is aggregated from indices for over 300 separate industries.
The indices published on this site are grouped according to the 2003 revised Standard Industrial Classification (SIC 2003). The four broad groupings of industries are:
(a) agriculture, hunting, forestry and fishing
(b) production
which comprises: mining and quarrying industries; energy and water supply; and manufacturing, which includes: refined petroleum products and nuclear fuel; chemical and man-made fibres; metal and metal products; engineering and allied industries; food, drink and tobacco industries; textiles, footwear, leather and clothing; other manufacturing.
(c) construction
(d) services
which includes: retail and wholesale; hotels and catering; transport, storage and communication; financial services; real estate and business services; public administration, education and health; other services.
Revisions
Very few statistical revisions arise as a result of 'errors' in the popular sense of the word. All estimates, by definition, are subject to statistical 'error' but in this context the word refers to the uncertainty inherent in any process or calculation that uses sampling, estimation or modelling. Most revisions reflect either the adoption of new statistical techniques, or the incorporation of new information which allows the statistical error of previous estimates to be reduced. Only rarely are there avoidable 'errors' such as human or system failures, and such mistakes are made quite clear when they do occur.
The figures in the latest Statistics Publication Notice incorporate revisions to previously published estimates. Tables 8 - 13 identify the extent of revisions since the previous publication. Revisions are shown to one decimal place for total GDP and GDP excluding oil & gas. Revisions are shown to zero decimal places for all other sectors.