Things get tricky when the definition of a spouse is changed, as it effects other areas of civil law. Take, for instance, private or government pensions.
Suppose that a man leaves his wife prior to retirement, and begins a commonlaw relationship with a gay lover. A cohabitant commonlaw spouse is recognized as the spouse over a person to whom the pension applicant is married to, but separated from. Legislation also requires that a pension be payable for the lifetimes of both the member and spouse, (Joint and Survivor),unless the spouse signs a waiver allowing for the pension to be payable in a different form.
In many cases, the pension benefits earned are in the form of a single life benefit, and the Joint and Survivor amount is an actuarial equivelent, (A reduced amount which takes into account the average life expectancies of persons from a given age onward, (mortality tables), the difference in age between the member and spouse, interest rates, etc.
The figures below have not been actuarially calculated, but they are a close approximation of what the results might be.
Let's assume that the member of a private company pension plan is age 60 at retirement, and the spouse is age 55. The pension is $1,000 per month, as a single life pension with 60 months guaranteed. For a J&S equivelent, payable for both lifetimes with 60% continuation to the spouse, (if living), on the member's death, the actuarially equivelent monthly pension amounts might be:
Member Male, Spouse Female: $880 per month.
Member Female, Spouse Male: $910 per month.
Member Male, Spouse Male: $930 per month
Member Female, Spouse Female: $830 per month.
The differences in actuarial equivelence are based almost entirely on the average life expectancies of Males and Females. It's a statistical fact that, on average, the age at death for a woman is 3-5 years later than that of a man.
I could see many members of a pension plan who are in a heterosexual marriage being upset if a co-worker, with equal accrued benefits, would receive a higher pension specifically because his spouse is of the same gender. I could also see lesbian couples being upset if their pension was more than 10% less than a gay male couple, all other things being equal.
If legislation required that actuarial tables be gender neutral, the lesbian couple would benefit most, as statistically one of the two women would live longer than a member or spouse in any of the other three pairs. Benefits to all might be, say, $870 per month, which would still favour the lesbian couple.
Otherwise, the pension plan might require additional contributions or reduced benefits to conform with the changes in actuarial assumptions. Then the benefit entitlements of a single plan member may be reduced, to offset additional benefits that would be payable to lesbian couples.
We also have to take into account that the determination of the spouse is made at the earlier of the date of retirement or the date of death, and does not take into account who was the spouse for the longest period of time.
Would pension plan members have to prove that they are gay, if being so would result in an enhanced benefit? Could a gay man diagnosed with AIDS have a marriage of convenience arranged, whereby another man would give him a lump sum of money, in exchange for the lifetime survivor pension on the member's death? Would someone be legally free to marry a person of the opposite sex if they are married to, but separated from, a person of the same sex? All of these problems come up when the definition of a spouse is changed.
A major reason why the Income Tax Act gives advantages to married or equivelent to married couples over singles is that heterosexual couples are more likely than singles to have children, who will become tomorrow's tax payers, and pay for the guaranteed government benefits such as CPP and OAP.
The same reasoning is in effect, (though no government will admit it), in immigration policy. Canada allows a higher number of immigrants from developing countries than it does from developed countries because of fertility rates. On average, persons of Asian and African descent have more children than those of European descent. A simple review of population density figures in an Atlas will confirm this.
In five years, the first of the baby boomers will be reaching age 65, and their numbers, as seniors, will steadily increase for 25-30 years thereafter.
Regardless of their contribution to the economy during their working years, senior citizens are a debit to tax dollars, in that they have higher medical bills, and receive payments from government pension, instead of making contributions.
Anybody who pays CPP contributions is not paying for their own future benefits, they're paying the benefits in force for people who have already retired, with the government's implied promise that, when they reach retirement age, persons younger than themselves will foot the bills. It's similar to a pyramid scheme, and it only works as long as the base of the pyramid, (young workers), is significanly larger than the peak, (retirees).
Of course CPP does not work on a paycheque to paycheque basis for benefits, and there is a large amount in the CPP fund, but it is severely underfunded in terms of assets vs future earned benefits. It can't sustain itself if the average couple, regardless of their gender, has less than two children.