In conventional kinship diagrams, we denote the relationship of marriage with a symbol like an double bar (\ or an underbar linking two people, usually a circle and a triangle. This sets of the relationship off from consanguineous relationships, and often indicates the boundaries between groups. It seems to suggest that this relationship of affinity is something that can be approached objectively, as though it exists independently of the people in it. Kinship diagrams are so reassuring. In spite of differences among cultures, the wordless symbols of affinity imply that, with apologies to Gertrude Stein, a marriage is a marriage is a marriage.

Some recent reports. Barely half of all US adults are married (Cohn et al. 2011). The average age of the first marriage in the US has been approaching 30 gradually for many years. In the 1960s, an overwhelming majority of 20-somethings were married. In 2008, only about 25% were (Pew Research Center 2010).

In Australia, women have tended to first enter into marriage at an older age than American women. The same or similar trends are visible in Australian society too (Australian Bureau of Statistics 2010).