My number is from from Stevenson-Wolfers (alt alt), particularly Figure 2, page 37. It is not a misinterpretation. To be more precise, about 50% of first marriages from the 70s made it to 25 years. First marriages from 80s appear to a do a little better, heading for maybe 55%, but it is too soon to tell [this previously said that it was too soon only because of binning decisions, but that's wrong; the problem is that the data was collected in 2001].
That paper also reflects the consensus of all the other resources I've been able to find in that the rate of divorce seems to be declining since the 70s; it may be too early to be overwhelmingly certain, but the evidence suggests that not only are the odds better for a marriage in the 1980s than the 1970s, but that the odds are better still in the 1990s, and then better than that in the 2000s.
Dalrock writes an interesting article related to Dr. Helen Smith's book the Marriage Strike. I really have to bump it up on my too rapidly growing reading list. (^_^)