Could you point to the comparison of the 2000s to the 1990s? As to the 90s vs the 80s, the difference is trivial.
That the rate has continued to fall through the 2000s I did not take from that paper, but from the other sources I encountered while searching for the raw statistics. A bit more searching suggests some disagreement on the state of the trend between different agencies.
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. (^_^)