Interest rates on short-term T-bills rose slightly.

The Treasury Department sold $8.03 billion in new three-month bills at an average discount rate of 5.23%, up from 5.18% last week. Another $8.01 billion was sold in new six-month bills at an average discount rate of 5.30%, up from 5.21% last week. The rates were the highest since Oct. 20, when three-month bills sold for 5.30% and six-month bills averaged 5.39%. The new discount rates understate the actual return to investors--5.37% for three-month bills, with a $10,000 dollar bill selling for $9,867.80, and 5.52% for six-month bills selling for $9,732.10. The discount rate reflects the price discount received when government securities are purchased at less than face value.