Journal of Economics

, Volume 109, Issue 3, pp 303–313 | Cite as

On inferior inputs and marginal returns

  • Paolo BertolettiEmail author
  • Giorgio Rampa


An input is inferior if and only if an increase in its price raises all marginal productivities. A sufficient condition for input inferiority under quasi-concavity of the production function is then that there are increasing marginal returns with respect to the other input and a non-positive marginal productivity cross derivative. Thus, contrary to widespread opinion, input “competitiveness” is not needed. We discuss these facts and illustrate them by introducing a class of simple production function functional forms. Our results suggest that the existence of inferior inputs is naturally associated with increasing returns, and possibly strengthen the case for inferiority considerably.


Inferior and normal inputs Marginal productivity Homotheticity 

JEL Classification

D11 D21 D24 


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Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  1. 1.Dipartimento di economia politica e metodi quantitativi, Facoltà di EconomiaUniversity of PaviaPaviaItaly

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