The Treasury Department auctioned $17 billion in three-month bills at a discount rate of 1.16%, and $15 billion in six-month bills was auctioned at a discount rate of 1.19%.
The three-month rate was down from 1.18% last week and was the lowest since three-month bills averaged 0.98% on July 28, 1958. The six-month rate was down from 1.23% last week and was the lowest rate on record.
The new discount rates understate the actual return to investors -- 1.179% for three-month bills, with a $10,000 bill selling for $9,970.70, and 1.22% for a six-month bill selling for $9,939.80.
In a separate report, the Federal Reserve said the average yield for one-year Treasury bills, a popular index for making changes in adjustable-rate mortgages, edged down to 1.38% last week from 1.41% the previous week.