Editing Substitution effect (section)

== Elasticity of substitution ==
The concept of the elasticity of substitution was developed by two different economists, each with their own focus. [[John Hicks]] defined elasticity of substitution—also known as the direct elasticity of substitution—as the percent change in the relative number of factors of production used given a particular percent change in relative prices or marginal products. [[Joan Robinson]] defined elasticity of substitution as the change in the ratio of the number of factors used divided by the change in the ratio of each factor's prices. These two definitions function in the same way when limited to two factors of production.<ref>Helm D.R. (2008) Elasticity of Substitution. In: Palgrave Macmillan (eds) The New Palgrave Dictionary of Economics. Palgrave Macmillan, London. {{doi|10.1057/978-1-349-95121-5_468-2}}{{page needed|date=April 2025}}</ref>{{full|date=April 2025}}