Short-term T-bill interest rates rose again.

The Treasury Department sold $7.81 billion in new three-month bills at an average discount rate of 5.55%, up from 5.51%last week. Another $7.82 billion was sold in new six-month bills at an average discount rate of 5.58%, up from 5.50% last week. The rates were the highest since Aug. 18, when three-month bills sold for 5.64% and six-month bills averaged 5.65%. The new discount rates understate the actual return to investors--5.71% for three-month bills, with a $10,000 bill selling for $9,859.70, and 5.82% for six-month bills selling for $9,717.90. The discount rate reflects the price discount received when government securities are purchased at less than face value.