On Wiles’s figures, German house prices in 2012 represented a 10 percent decrease in real terms compared to thirty years ago. That is a particularly astounding performance compared to the UK, where real prices rose by more than 230 percent in the same period. (Wiles’s commentaries can be read here and here.)
A key to the story is that German municipal authorities consistently increase housing supply by releasing land for development on a regular basis.
If you don’t release land, then prices can go only one way. You need to do more than just release land but nothing else will work if you don’t do that.