Since the outbreak of the financial crisis, European countries have been divided into two groups: the risky countries and the safe havens. Germany has been the most important member of the latter group, of course. This has caused the demand for German Treasury bonds (Bunds) to soar. That's why yields (interest rates) have fallen significantly.
Recently, the Bund yields reached its historical lows making the German state debt service cheaper:
According to the Federal Minister of Finance, Mr. Wolfgang Schäuble, Germany's public budgets have saved about EUR 120 billion since the outbreak of the crisis:
Similarly, German households have enjoyed cheaper mortgages and German corporations have taken the advantage of cheaper investment loans.