That is less than the overnight borrowing rate among banks, set by the Federal Reserve at 5.5 percent.
By contrast, German long-term borrowing rates, at 7.35 percent, carry a cost over inflation of only 3.7 percentage points.
But the banks have not passed on the lower borrowing rates to their customers.
Lower borrowing rates on many consumer loans are expected as a result of the rate reduction.
Italy had to pay higher borrowing rates in its last bond auction of the year on Wednesday.
There is confidence, as well, that Mexican borrowing rates will fall further.
But the blow, soft as it was, will be felt all through the economy by lifting borrowing rates.
If the Treasury's own borrowing rate averaged 8 percent, the $20,000 debt would be cleared in 12 years.
When bond investors sour on a company's prospects, higher borrowing rates are a result.
And with adjustable rate mortgages, the borrowing rate is even lower.
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