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. 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 26% were (Pew Research Center 2010). The same or similar trends are visible in Australian society too (Australian Bureau of Statistics 2010).

In many western countries, especially since the 1960s, the conventional wisdom has been that the traditional family is breaking down. This has been interpreted as both a good and a bad thing, but most people agreed that a loosening of traditional morality was the cause of these trends. International comparisons are striking here. While all societies have some rate of divorce, divorce is much more likely in some countries than others.