But the Fed is not really sure what is driving the sharp rise in long-dated bond yields, and especially a widening gap between short and long term yields.

Do rising U.S. Treasury yields and a steepening yield curve suggest an economic recovery is more certain, meaning less need for safe haven government bonds and a healthy demand for credit? If so, there might be less need for the Fed to expand the money supply by buying more U.S. Treasuries.

Or does the steepening yield curve mean investors are worried about the deterioration in the U.S. fiscal outlook, or the potential for a collapse in the U.S. dollar as the Fed floods the world with newly minted currency as part of its quantitative easing program. This might be an argument to augment to step up asset purchases.