Statistical evidence across the population and in every country studied, underline my argument that wives are doing more than any other group of women. They are the closest to men in most aspects of productivity or politics, for that reason.

Their marriage lessens the load of any particular responsibility, but it also expands their responsibilities far beyond the scope that unmarried women are expected to carry. They are therefore more likely to struggle under the weight of their own responsibilities, if their husband can't carry his half (death, divorce, disability, unemployment, etc.), or one of their responsibilities becomes a particularly heavy burden, by circumstances or their own personal decline/aging.

Being a wife arguably has a bigger impact on a woman's entire existence, than even motherhood does, and wives are more likely to be mothers and to have more children, on average. Wives are also more-likely to care for elderly or disabled family members because marriage expands the number of such family members that they have.