Facts
P. [B.], born in 1922, and F. [C.], born in 1928, were married on April 3, 1992. Prior to their marriage, they were both in receipt of a single old-age pension. The wife's pension, based on the pension scale 44, amounted to 1,800 francs per month. The husband's pension, calculated according to the pension scale 40, amounted to 1,636 francs.
By two decisions dated May 25, 1992, the Vaud Cantonal Compensation Fund allocated to each spouse, in replacement of the single pensions they were receiving, a half-ordinary old-age pension for couples of 1,228 francs per month, effective May 1, 1992. The couple's pension was calculated based on an average annual income of 154,440 francs and a contribution period of 34 years and 10 months, resulting in the application of the pension scale 40.
F. and P. [B.] appealed against this decision, concluding that they should be paid a pension corresponding to the total amount of the pensions that each spouse would have received if they had not married. Subsidiarily, they concluded that a couple's pension should be paid based on the pension scale 44 (full pension).
By judgment of January 21, 1993, the Insurance Court of the Canton of Vaud dismissed the appeal.
Against this judgment, the [B.] spouses filed an administrative law appeal in which they reiterated their previous conclusions.
Considerations
a) The compensation fund was right, in view of the legal regulations, to replace the single pensions received by the appellants with a couple's pension, the calculation of which, moreover, is in accordance with the law.
Indeed, due to his marriage to F. [C.], who had then reached the age of 62, the appellant was entitled to an old-age pension for couples (Art. 22 para. 1 OASI) succeeding the single old-age pensions previously granted to the spouses (Art. 21 para. 2 OASI). The couple's pension was paid in equal shares to each spouse, in accordance with Art. 22 para. 2 OASI. As for the calculation of the couple's pension, it was carried out, in accordance with Art. 32 OASI, on the basis of the husband's average annual income, taking into account the income from gainful employment on which the wife had paid contributions (Art. 32 paras. 1 and 2 OASI). In this calculation, it is the husband's contribution period that is decisive (Art. 32 para. 1 OASI in correlation with Art. 30 para. 1 OASI), hence the application in this case of the pension scale 40 (and not 44).
b) The appellants argue that the aforementioned regulations result in unequal treatment between married couples and cohabitants. They also argue that these regulations violate Art. 4 para. 2 Cst., in particular due to the fact that the couple's pension is calculated on the basis of the pension scale applicable to the husband and not on the more favorable scale applicable to the wife.…