Yes, but to get a good picture one should account for how large the geographic separation between the couples is and for what reasons? The case of spouses volun

Yes, but to get a good picture one should account for how large the geographic separation between the couples is and for what reasons? The case of spouses voluntarily living apart on either coasts of the continental USA for career reasons or to save time commuting is quite different from that of a couple within tens of miles of each other, separated involuntarily due to affordability.