摘要：There is a continuing need to use recent and consistent multisectoral economicdata to support policy analysis and the development of economywide models. Updating andestimating input-output tables and Social Accounting Matrices (SAMs) for a recent year is adifficult and a challenging problem. Typically, input-output data are collected at long intervals(usually five years or more), while national income and product data are available annually, butwith a lag. Supporting data also come from a variety of sources; e.g., censuses of manufacturing,labor surveys, agricultural data, government accounts, international trade accounts, andhousehold surveys. The problem in estimating a SAM for a recent year is to find an efficient (andcost-effective) way to incorporate and reconcile information from a variety of sources, includingdata from prior years. The traditional RAS approach requires that we start with a consistent SAMfor a particular period and "update" it for a later period given new information on row andcolumn sums. This paper extends the RAS method by proposing a flexible entropy differenceapproach to estimating a consistent SAM starting from inconsistent data estimated with error, acommon experience in many countries. The method is flexible and powerful when dealing withscattered and inconsistent data. It allows incorporating errors in variables, inequality constraints,and prior knowledge about any part of the SAM (not just row and column sums). Since the input-output accounts are contained within the SAM framework, updating an input-output table can beviewed as a special case of the general SAM estimation problem. The paper presents thestructure of a SAM and a mathematical description of the estimation problem. It then describesthe classical RAS procedure and the entropy difference approach. An example of the entropydifference approach applied to the case of Mozambique is presented. In addition, an appendixincludes a listing of the computer code in the GAMS language used in the procedure. Paper presented at the MERRISA (Macro-Economic Reforms and RegionalIntegration in Southern Africa) project workshop. September 8 -12, 1997, Harare, Zimbabwe. Our thanks to George Judge, Amos Golan, Hans L.fgren,and workshop participants for helpful comments on earlier drafts
