9.1 The ASNA includes symmetric input-output tables (for the definition of 'symmetric' see paragraph 9.2) as well as closely related supply and use (S-U) tables. Both types of tables are known as input-output tables. Input-output tables provide a means of undertaking detailed analysis of the process of production and the use of goods and services (products), and of the income generated in that production. The concepts and definitions used for the S-U tables and the input-output tables of the ASNA are the same as in the rest of the system. For a detailed discussion of the nature of input-output and supply and use tables see Chapter 15 of SNA93.
9.2 The integration of 'input-output' in the overall system of national accounts is an important feature of the ASNA. Its role in the ASNA is primarily related to the goods and services accounts and to the shortened sequence of accounts for industries. Complementing the full sequence of accounts for institutional sectors, which cover all kinds of accounts in the ASNA, the S-U tables, and subsequently the symmetric input-output tables, serve to provide a more detailed basis for analysing industries and products through a breakdown of the production account, and the generation of income account and the goods and services account, leading to the symmetric input-output table. 'Symmetric' means that the same classifications or units (e.g. the same groups of products) are used in both rows and columns. When the number of rows of products and columns of industries in S-U tables happens to be equal, they are referred to as square (not symmetric) S-U tables. However, S-U tables are most often rectangular (having more products than industries).
9.3 The input-output tables, and in particular the S-U tables, serve two purposes: statistical and analytical. They provide a framework for checking the consistency of statistics on flows of goods and services obtained from quite different kinds of statistical sources - industrial surveys, household expenditure inquiries, investment surveys, foreign trade statistics, etc. The ASNA, and the input-output tables in particular, serve as a coordinating framework for economic statistics, both conceptually for ensuring the consistency of the definitions and classifications used and as an accounting framework for ensuring the numerical consistency of data drawn from different sources. The input-output framework is also appropriate for calculating much of the economic data contained in the national accounts and detecting weaknesses. This is particularly important for the decomposition of the values of flows of goods and services into prices and volumes for the calculation of an integrated set of price and volume measures. As an analytical tool, input-output data are conveniently integrated into macroeconomic models in order to analyse the link between final demand and industrial output levels. Input-output analysis also serves a number of other analytical purposes or uses.
9.4 A fundamental role is played in the ASNA by S-U tables. They show, for the economy as a whole and for groups of products, the total resources in terms of domestic output and imports, and the uses of goods and services in terms of intermediate consumption, final consumption, gross capital formation and exports. They also provide information on the generation of income from production.
9.5 The symmetric input-output tables are also an important part of the ASNA, serving as a well-established tool for various analytical purposes related to production.
9.6 The symmetric input-output tables are generally based on S-U tables. However, as the latter are data-orientated in nature, adjustments are required in the compilation in the former, particularly with respect to valuation, the treatment of imports and classifications. Readers interested in a detailed description of constructing symmetric input-output tables should refer to the Handbook on Input-Output Table Compilation and Analysis published by the Statistics Division Department of Economic and Social Affairs of the United Nations.