...Investors appear willing to buy at these rates because of falling inflation in Europe. There are even concerns about deflation, which could trigger bigger problems like a recession. The idea is that these German bonds would lose less value than other assets.
...That deterioration is due to upcoming moves by the European Central Bank. The ECB is hoping to fire up the region's ailing economy by launching a massive bond-buying program next month, which will almost certainly drive down European bond yields further. Investors have already been fleeing the euro in search of better returns elsewhere.