Concerning the German housing data; keep in mind

(1) rents are regulated and cannot grow quickly, so it would make sense to look at whether rents grow too slowly rather than houses rising too quickly in price.

(2) always be careful about graphs of this kind, with indexing at a specific date

(3) house property may rise in value due to restricted ground for construction - especially in those cities. City councils know about demographics and do not develop many new areas for settlement any more. A rising price as reflection of a scarcity is fine and not a bubble.

(4) the interest rate data is about requested loans, not granted ones

(5) housing in cities such as Munich, Frankfurt and Berlin is not only very different to housing in towns nearby, but also very atypical for German housing in general.

(6) Income levels in business are higher in Frankfurt and Munich than elsewhere, in order to compensate for higher cost of living there.

(7) a short-term look back only to the beginning of the crisis is a dubious choice. I'd rather ask for data reaching back to '90.