You have to ask if the term marriage includes de facto relationships as you have to remember that human social behavior, patterns of social relationships, social interaction, and aspects of culture tend to change with the passing of time.
Here, for instance, one has also to ask if that alleged decrease in the numbers of people seeking "legal" marriage is out of economic necessity or simple because of an increase in the number of independent carrier women.
And remember, with all else being equal, if the number of those getting married is going down then the number of those staying single must be going up.
