There's been a lot of speculation on why this is happening. ZH claims this will reverse in the next few weeks. The Fed increases its excess reserves account to offset the drop in Treasury's cash balance as they burn through cash. The Fed's reserve balance is used to determine the weekly monetary base.
http://www.zerohedge.com/article/no...t-surge-adjusted-monetary-base-past-two-weeks
Although QE2 is over the Fed is still reinvesting principal payments, like a mini QE. I think they will continue this and launch QE3 if we fill those gaps around SPX 1100.
"Under the existing reinvestment policy, principal payments from agency debt and agency mortgage-backed securities (MBS) are reinvested in longer-term Treasury securities. In implementing this policy going forward, the Desk will follow operating practices similar to those established during the $600 billion Treasury purchase program."
http://www.newyorkfed.org/markets/tot_operation_schedule.html
