Functional forms, exogenous shifts, and economic surplus changes

Xueyan Zhao, John D. Mullen, Gary R. Griffith

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12 Citations (Scopus)


Conditions for exact welfare measures in equilibrium displacement modeling are examined. These relate to the functional form of supply and demand, the nature of the exogenous shift, and the definition of percentage changes. Approximation errors when these conditions are not met in empirical applications are investigated and analytical expressions for the errors derived. Significant errors are possible when a proportional shift is assumed. The assumptions underlying Alston and Wohlgenant's empirical findings are identified. The restriction that supply must be elastic is shown to be unnecessary.

Original languageEnglish
Pages (from-to)1243-1251
Number of pages9
JournalAmerican Journal of Agricultural Economics
Issue number4
Publication statusPublished - 1997
Externally publishedYes


  • Economic surplus
  • Equilibrium displacement modeling
  • Exogenous shift
  • Functional form

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