Editing Edgeworth box (section)

===Uniqueness of equilibria===
[[File:Edgeworthpathology1.svg|280px|thumb|left|Fig. 10. An Edgeworth box with multiple equilibria]]
[[File:Edgeworthpathology2.svg|280px|thumb|right|Fig. 11. An Edgeworth box with multiple equilibria (detail)]]
It might be supposed from economic considerations that if a shared tangent exists through a given endowment, and if the indifference curves are not pathological in their shape, then the point of tangency will be unique. This turns out not to be true. Conditions for uniqueness of equilibrium have been the subject of extensive research: see [[General equilibrium theory#Uniqueness|General equilibrium theory]].

Figs. 9 and 10 illustrate an example from Mas-Colell et al. in which three distinct equilibria correspond to the endowment point '''ω'''. The indifference curves are:

<math>\quad x - \tfrac{1}{8}y^{-8} = u</math> (Octavio)

<math>\quad y - \tfrac{1}{8}x^{-8} = u</math> (Abby).

The indifference curves fill the box but are only shown when tangential to some representative budget lines. 
The offer curves, drawn in Fig. 11, cross at three points shown by large grey dots and corresponding to exchange rates of {{frac|1|2}}, 1 and 2.