For one thing, it is hard to know how much companies have in fact lengthened the maturity of their debts because the interest-rate swap market allows them to swap those fixed bond payments into cheaper floating debt, a popular strategy in the investment-grade market.

ECONOMIST: Better to feast on cookies than junk bonds

Another reason demand for the long bond has been so voracious is that a lot of investment banks still use them to hedge their corporate-bond positions and interest-rate swaps (between fixed- and floating-rate obligations).

ECONOMIST: Bond bombshell

The fact that early bonds had no fixed maturity date ensured that any change in interest rate was fully reflected in the capital value of the bond.

ECONOMIST: What did early 19th-century literary characters live on?

With bond yields rising since the Fed announced QE2, 30-year fixed rate mortgage interest rates went up to their highest level since the week of September 30 to 4.46%.

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