With interest rates flirting with 3% on the 10-year Treasury note, and the potential (and eventuality) that they will go significantly higher, I thought it might be timely to review a blog post from February 10, 2013 called “Limits on the 500-pound Gorilla.” (It’s worth reading that original post for some of the comments attached thereto.)

Well, here’s an interesting little tidbit. (But first, a note from our sponsors: some channels didn’t pick up my article from  last Wednesday, “Fun With The CPI,” so follow that link if you’d like to read it.)

The Fed adds permanent reserves by buying securities, as we all know by now. The Open Market Desk buys securities and credits the Fed account of the selling institution. Conversely, when the Fed subtracts reserves permanently, it sells securities and debits the account of the buying institution.

As of February 6th, the Fed owned $1.782 trillion in face value of Treasury and agency mortgage-backed securities. At the closing prices from Friday, those securities are worth $2.069 trillion, plus accrued interest which I didn’t bother to calculate.

So let’s revisit for a second the question of how the Fed would unwind the quantitative easing and actually tighten policy. In order to do that, the Fed would first need to vaporize the $1.58 trillion that exists in excess reserves, before they could actually affect the required reserves which is where the rubber meets the road for monetary policy (at least, in the absence of the “portfolio balance channel”).

We have reviewed some of the options before: sell the securities held in the System Open Market Account (SOMA); conduct massive and long-dated repo operations; sell bills or pay interest on deposits at the Fed (or raise IOER). Some people have suggested that the Fed could just “let the securities in the SOMA roll off”: i.e., let the bonds mature and don’t reinvest the proceeds. I was curious how long, after Operation Twist, such a passive approach would take.