Why do interest rates fluctuate so wildy?
OK, this is a bit complicated. If you look every month at the interest paid on the debt, you’ll see that it is much higher in some months than in others, even though the size of the debt changed very little. The explanation is in the way the Treasury Department sells and redeems securities. They sell securities several times every month. Some securities mature in as little as four weeks, others in as long as thirty years Every month, some securities mature and are redeemed. Some of those will have been sold in the previous month, but some were sold thirty years ago. Study Table PDO-1, Maturity Schedules of Interest bearing Securities, which is linked from the Treasury Bulletin website. It lists all the market offerings of securities that are still outstanding, and their issue dates and interest rates —all sorted by the dates they mature. Notice that the interest rates on individual lots of securities can be as low as 1.5%, and as high as 14%. Refer also to the Monthly Interest Rate Cer
