Since the United Nations introduced the nonsymmetrical make-use input-output (I-O) tables in 1968, there have been on-going discussions about ways to translate them into symmetric I-O tables. The discussions have focused on secondary products that cause the asymmetry between industries and commodities and two alternative assumptions, the industry-technology assumption (ITA) and the commodity-technology assumption (CTA), which have been used for their transfer between industries. Despite much debate and discussion over the years, no definitive consensus has emerged as to which is superior.
For the 1992 Benchmark I-O Tables, the BEA prepared and published two sets of make-use tables, which provide alternative presentations of a large subset of secondary products. For one set of tables, the outputs and inputs of secondary products with distinctive production processes compared to those of primary products produced by industries were moved “by hand” to where they are primary, using the CTA. In this paper, the authors use the two formats to compare the different results of using two assumptions to derive symmetric I-O tables. The differences are then evaluated.