Figure 1 shows that the three-month Treasury yield varied from highly unresponsive to more than normally responsive to macroeconomic news between 2001 and 2012. From the spring of 2009 through the end of 2012, the yield was either partially or completely insensitive to news. It is natural to interpret this insensitivity as stemming from the zero lower bound, since the federal funds rate and three-month Treasury yields were both essentially zero from December 2008 through the end of our sample. Thus, our analysis finds that the zero lower bound substantially constrained Treasury yields at the shortest end of the yield curve from the spring of 2009 onward, as one would expect.