These are based on Max Anderson's Net Liquidity model.
The formulas for each band are:
(FRED:WALCL-FRED:WTREGEN*1000-FRED:RRPONTSYD*1000)/1000/1.1-1625 + 350
(FRED:WALCL-FRED:WTREGEN*1000-FRED:RRPONTSYD*1000)/1000/1.1-1625 - 150
The formulas for each band are:
(FRED:WALCL-FRED:WTREGEN*1000-FRED:RRPONTSYD*1000)/1000/1.1-1625 + 350
(FRED:WALCL-FRED:WTREGEN*1000-FRED:RRPONTSYD*1000)/1000/1.1-1625 - 150