A negative German GDP reading has triggered drop in confidence in European growth projections. This has lead to a shift into the safety of U.S. Treasury Bonds. Buying has pushed the T-Bond prices higher and therefore a lower yield. So low, that the 10 year T-Bond yield has pushed below the 2 year T-Bond, thus inverting the yield curve, with longer dated yields now below short term yields. Historically this situation has been a harbinger of a potential economic recession.