As sociologist Andrew Cherlin stated in his recent book The Marriage-Go-Round, “Both marriage and divorce contribute to the larger picture of a country (the U.S.) in which people partner, unpartner and repartner faster than they do in any other Western nation.” When it comes to intimate partnerships, Americans seem to be on speed.

After a divorce, as Cherlin notes, ex-spouses in this country seem to find a new partner more quickly than happens in other nations. They often form cohabiting (livi...