The expectation of an increase in interest rates has been causing the shorter-term bonds to increase, while the longer-term bonds have remained stable over the past month. The strong indication of this is the significant decrease of 1.8 basis points, which illustrates the demand for longer-dated bonds. Another factor contributing to this is the difference between the rates of the 20-year and 30-year bonds, with the former having a rate of 4% and the latter having a rate of 3.83%.