As a mostly single earner in a community property state, my spouse earns half the income for tax purposes. If you were going to tax individuals, it's probably reasonable to apply income evenly across marriages for all states.
I supported a non-earning spouse for a decade in Canada and it's always been a bit murky. Like in 2014-2015 there was a concept of transferring up to 50k of income to the spouse ("Family Tax Cut"), but Trudeau's Liberal gov't canceled it when they came into power; I think they correctly recognized that it was basically a handout to families privileged enough to be in a position where there was enough spread between the two earners that transferring that sum would be significant.
CRA is even pretty careful about letting a spouse claim capital gains income; it's always attributed back to whoever earned the original principal (outside of inheritance). I think the only way around this is to formally "loan" the spouse their investment money, but you have to charge them interest and the interest is of course income to you.
I supported a non-earning spouse for a decade in Canada and it's always been a bit murky. Like in 2014-2015 there was a concept of transferring up to 50k of income to the spouse ("Family Tax Cut"), but Trudeau's Liberal gov't canceled it when they came into power; I think they correctly recognized that it was basically a handout to families privileged enough to be in a position where there was enough spread between the two earners that transferring that sum would be significant.
CRA is even pretty careful about letting a spouse claim capital gains income; it's always attributed back to whoever earned the original principal (outside of inheritance). I think the only way around this is to formally "loan" the spouse their investment money, but you have to charge them interest and the interest is of course income to you.