There's a reported substantial upswing, in France, of young opposite-sex couples electing to contract "civil unions" instead of marrying. The French 1999 "pacte civil de solidarité" ("civil union") statute was apparently originally enacted, (as with the "civil union" and "domestic partnership" laws of several American states), as a"sort-of-marriage" for same-sex couples, but, as the New York Times reports, as of last year, 95% of the civil unions contracted in France were between mixed-sex couples.
P.S.: My thought, two months after I originally posted this, is that I'd like to know what happened to the marriage rate for the mixed-sex couples of the same age group during this period. Is it possible that having this option available for mixed-sex couples who were reluctant to marry, as the anecdotes suggest, actually increased the number of mixed-sex couples who were willing to make some sort of formal commitment?