From Guntram Wolff, originally published in Die Welt:
….what drives this decline in real interest rates? Real rates are determined by a whole set of economic factors, including growth prospects. Ultimately, it is economic performance that drives the return in investments. In a fast growing economy that is still building up its capital stock, real rates should be high as economic growth prospects are high. The opposite is true for an economy in a recessionary environment or an economy with already high capital stocks.