A recent article in the German newspaper “Die Zeit” (in German) describes the inflationary granting of a doctorate due to the formal need for a high rate of PhDs and “excellence” of universities – whatever this might mean. One measure for this opaque expression is a high ratio of PhD students per professor, naturally encouraging to hire as many PhD students as possible.
As a result of this development, plenty of new PhD students theses are elborated without stringent quality control, thus yielding limited to no ouput for the scientific world. This results in a severe decrease in academic productivity in two ways: First, PhD students with a topic of little relevance restrict themselves from being productive in another position; and second, they keep their supervisors off doing other and more useful research by causing much administration and supervision overhead.

So the questions are:
- How can we make sure that PhD research is of high quality?
- How many PhD students does a country even need, and what for?

Here’s the link to the full article:
http://www.zeit.de/studium/hochschule/2013-04/promotionen-anstieg-studentenzahlen