This is the method used by the central bank to control market interest rates in areas with market-oriented interest rates. Commercial banks pursue profit maximization and maintain a balance of account settlement funds within a certain period of time, so market interest rates will inevitably fluctuate between the upper and lower limits.

If the target interest rate set by the central bank is: r (for example, 4%), it will set the re-lending interest rate of commercial banks in the central bank to: r+s (for example, 5%, upper limit). At the same time, it will set the The deposit interest rate at the central bank is: r-s (for example, 3%, lower limit).