Editing David Ricardo (section)

===New interpretation===
Ricardo's four magic numbers have long been interpreted as comparison of two ratios of labour (or other input in fixed supply) coefficients. This interpretation is now considered as overly simplistic by modern economists. The point was rediscovered by Roy J. Ruffin<ref>Ruffin, R.J. (2002) David Ricardo's discovery of comparative advantage. ''History of Political Economy'' 34(4): 727–748.</ref> in 2002 and re-examined and explained in detail in Andrea Maneschi<ref>Maneschi, A. (2004) The true meaning of David Ricardo's four magic numbers. ''Journal of International Economics'' 62(2): 433–443.</ref> in 2004. The more flexible approach is now known as the ''new interpretation'', despite having been previously mentioned by [[Piero Sraffa]] in 1930 and by Kenzo Yukizawa in 1974.<ref>Tabuchi, T. (2017) Yukizawa's interpretation of Ricardo's 'theory of comparative cost'. In Senga, Fujimoto, and Tabuchi (Eds.) ''Ricardo and International Trade'', London and New York; Routledge, Chapter 4, pp. 48–59.</ref> The new interpretation affords a totally new reading of Ricardo's ''Principles of Political Economy and Taxation'' with regards to trade theory, although it does not change the mathematics of optimal resource allocation.<ref>Faccarello, G. (2017) A calm investigation into Mr. Ricardo's principle of international trade. In Senga, Fujimoto, and Tabuchi (Eds.) ''Ricardo and International Trade'', London and New York; Routledge. Tabuchi, T. (2017) Comparative Advantage in the Light of the ''Old'' Value Theories. In Shiozawa, Oka, and Tabuchi (eds.) ''A New Construction of Ricardian Theory of International Values'', Tokyo: Springer Japan, Chapter 9 pp. 265–280.</ref>