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Production Function Geometry With "Knightian" Total Product


  • Dale B. Truett
  • Lila J. Truett


Abstract: Authors of principles and price theory textbooks generally illustrate short-run production using a total product curve that displays first increasing and then diminishing marginal returns to employment of the variable input(s). Although it seems reasonable that a temporary range of increasing returns to variable inputs will likely occur as variable inputs are added to a set of fixed ones. This proposition implies an isoquant diagram that is not a familiar one in text-books. The authors examine a linearly homogeneous production function conforming to the textbook case and construct its isoquant diagram. They then use a geometrical proof attributable to Geoffrey Jehle (2002) to demonstrate that, in general, isoquants must have, outside the traditional ridge lines, a range where they are convex toward those ( MP = 0) ridge lines and another range where they are concave toward them if there are short-run increasing, then diminishing, marginal returns. The authors suggest how this issue might be presented to students.

Suggested Citation

  • Dale B. Truett & Lila J. Truett, 2006. "Production Function Geometry With "Knightian" Total Product," The Journal of Economic Education, Taylor & Francis Journals, vol. 37(3), pages 348-358, July.
  • Handle: RePEc:taf:jeduce:v:37:y:2006:i:3:p:348-358
    DOI: 10.3200/JECE.37.3.348-358

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