On the first row of result images in the "divorce rate" search you posted there are 5 graphs. 2 of them measure "divorces per 1000 people", and 3 measure "divorces per 1000 marriages".
In the divorce per 1000 marriages case, it would appear to be independent of the marriage rate.
a) Divorce rates are actually decreasing
b) They aren't independent of the marriage rate though (as the marriage rate is decreasing for the people most likely to get divorced)
On the first row of result images in the "divorce rate" search you posted there are 5 graphs. 2 of them measure "divorces per 1000 people", and 3 measure "divorces per 1000 marriages".
In the divorce per 1000 marriages case, it would appear to be independent of the marriage rate.