It has been going on for a long while, since the '60s. Guenter Glass, the novelist, wrote a book about the shrinking German population, predicting that by 2050, relatively few would be left.
The eneration after the war had children, but the next did not, preferring to enjoy their creature comforts. Many houses were built as three-generation houses, but, at least in the area near an American air base, they were more and more rented to Americans for the money. For the children had no children. Houses were built, but for one’s own amusement, to be left, perhaps to a nephew or niece. There is, I think, a deep pessimism in the country, based on an unexpressed atheism and the feeling that they have nothing to pass on, nothing worth passing on.