A recent paper sponsored by the Brookings Institution argues that the Treasury undermined the Fed's QE efforts by lengthening its debt. It is true that the debt lengthened, and it may be true that this put some upward pressure on interest rates, but if you look closely at the market activity of both entities you will see that Treasury actually kept well out of the Fed's way in the market. The Treasury continued to sell mostly at the short end while the Fed bought mostly in the 5-10 and 25-30 year ranges. The authors of the Brookings paper seemed to miss this because they focused primarily on aggregate measures of portfolio length, and they may not have realized that front-loaded portfolios like the Treasury's have a built-in tendency to lengthen.For more, see my blog post Getting it Wrong on the Treasury and the Fed.By the way, my analysis was recently cited by Matt Klein of FT Alphaville: The Real Reasons Why the US Treasury's Debt Maturity Has Been Rising