National IOTs are generally used to produce regional or international IOTs required for the estimation of TiVA. Sometimes detailed national IOTs are not available for small economies. In such cases, experts estimate the tables using different technology assumptions at the industry and product levels (UNCTAD, 2013a). Such assumptions may be obtained from the provider of the national data.
Even if national IOTs or SUTs contain high levels of detail, they do not provide information on the sources of imports or export destinations for each industry. Therefore, in the process of creation of the international IOT apart from the national IOTs/SUTs one also needs a database on bilateral trade data for all countries involved. This information is needed to allocate imports and exports to each industry in every economy. Along the bilateral trade statistics, a number of important assumptions and adjustments are also needed (OECD-WTO, 2012). Figure 6 shows a simplified international IOT with only two-countries and one industry.