Input-Output economics is that rara avis in economics, a genuinely new and original idea. It was not without precursors and Leontief has always been at least adequately generous in acknowleding them…. The fundamental discovery that distinguished Leon- tiefs work from that of all his predecessors is that it was practical to calculate the input-output coefficients from recorded data, to perform the necessary algebraic manipu- lations, and to use the results to answer a wide variety of practical economic questions' (Dorfman, 1973; pp. 430-31).