The "institucional" model of marriage has been overwritten by the "soul mate" model, which sees marriage as primarily a "couple-centered" vehicle for personal growth, emotional intimacy, and shared consumption that depends for its survival on the happiness of both spouses.
at page 71
key finding: The American divorce rate today is nearly twice that of 1960, but it has declined since hitting the highest point in our history in the early 1980s. The average couple marrying for the first time now has a lifetime probability of divorce or separation somewhere between 40 and 50 percent.
graphics at pages 19, 20, 40 and 70
See also the previous post "about divorce statistics at eHarmony"
More of "Trends in Marriage, Cohabitation, and Divorce" at eHarmonyLabs