[john_b]

I should have been more specific. I didn't mean that the probability of a marriage surviving some fixed time interval decreases linearly with the duration of the marriage. Everyone knows that marriages that have lasted longer are less likely to end than newer marriages. What I meant is that the cumulative probability of a marriage surviving decreases roughly linearly from the 5 year point onward, as Tables 5 & 6 show (and Fig. 4 shows graphically).

As an unmarried person, it's the latter that is of concern to me. If I had been married for 15-20 years already, the probability you cite would be more pertinent.