The current, rather mild U.S. recovery has been driven by asset appreciation/consumption and not employment or capex [capital expenditure] growth. Future growth is dependent on additional asset appreciation in real estate and stocks if Asia continues to absorb much of our investment and many of our jobs.
If Fed Funds were expected to rise in the future, the curve would be positive with intermediate and long bonds requiring higher yields as a cushion against accelerating short rates. If the Fed were expected to lower rates, a flatter, even inverted curve might result. It's not that this academic theory has been dislodged in recent years but it may have been asked to take a seat next to the increasingly important variable of global financial flows. These flows, no doubt, rely critically on the willingness of foreign investors to hold U.S. assets in the face of potential currency and asset price depreciation.