What is the test for varying spousal support?

Hickey v. Hickey, 1999 CanLII 691 (SCC), [1999] 2 S.C.R. 518 (S.C.C.) discussed the principles to be applied on an application to vary spousal support. I will paraphrase, quoting largely from that judgment at paragraphs 20 - 24: 1. On an application for a variation of an award of spousal support, the court must first find, under s. 17(4), that there has been a material change in the conditions, means, needs, or circumstances of either spouse. 2. Once this threshold is passed, the court must consider the four objectives of spousal support enumerated in s. 17(7) of the Divorce Act. 3. The objectives set out in s. 17(7) parallel those set out in s. 15.2(6) and reflect the principle that the economic consequences of the marriage and of the separation and divorce should be equitably shared between the former spouses. 4. The exercise of judicial discretion requires an examination of all four objectives set out in the Act in order to achieve equitable sharing of the economic consequences of marriage or marriage breakdown. This implies a broad approach with a view to recognizing and incorporating any significant features of the marriage or its termination which adversely affect the economic prospects of the disadvantaged spouse. 5. Neither the Act itself, nor the principles set out in Moge impose a single model for determining or varying spousal support. It is not a question of either one model or the other. It is rather a matter of applying the relevant factors and striking the balance that best achieves justice in the particular case before the court. 6. Where it is not possible to determine the extent of the economic loss of the disadvantaged spouse ... the court will consider need and standard of living as the primary criteria, together with the ability to pay of the other party.