Interest rates on 52-week bills sold by the Treasury declined at yesterday's auction, in contrast with an increase in three-month and six-month bill rates on Wednesday. Treasury sold $5 billion of 52-week bills at a discount rate of 14.58 percent, down from a record 15.056 percent on Sept. 3 and the lowest level since 14.542 percent on Aug. 7.

More important to many savers, the annual investment yield on the bills sold yesterday was 17.34 percent. This translates into an annual return for the new All Savers certificates of 12.14 percent compared with the current level of 12.61 percent. The old rate expires Saturday night and the new, lower rate is effective for certificates sold starting Monday morning.

All Savers rates are equal to 70 percent of the annual investment rate but the rate changes each month, based on results of the most recent 52-week bill auction. The coupon-equivalent rate on bills sold yesterday was 16.65 percent, down from 17.26 percent a month ago. Both the investment and coupon-equivalent rates, measuring yields for a year, are higher than the discount rate, since purchasers in effect get a refund (discount) on the initial purchase price.