Investors and those following the movement of interest rates look at the movement of Treasury yields as an indicator of things to come. Their rates are considered an important benchmark: Because Treasury securities are backed by the full faith and credit of the U.S. Treasury, they represent the rate at which investment is considered risk-free. The yield on 91-day Treasury bills is the average discount rate. How it's used: The rate is used as an index for various variable rate loans, particularly Stafford and PLUS education loans. Rates & Terms. Treasury bills are issued for terms of 4, 8, 13, 26, and 52 weeks. Another type of Treasury bill, the cash management bill, is issued in variable terms, usually of only a matter of days. 4-week, 8-week, 13-week, 26-week, and 52-week bills are auctioned on a regular schedule. Cash management bills aren't auctioned on a regular schedule.