The construction of symmetric input-output tables (SIOTs) is a controversial issue as regards the choice of model to construct both product-by-product and industry-by-industry SIOTs, especially the former ones. However, there has been little attention paid so far by the UN and the Eurostat Systems of National Accounts on the choice of type of SIOT to carry out impact analyses let alone other input-output applications. Concerning the price and quantity models in input-output analysis, this paper identifies severe problems in the correct interpretation of the meaning of their results and proposes the use of supply and use tables instead of SIOTs to solve these problems