The series is calculated by the Federal Reserve Bank of St.Louis.
Prior to 2003-01-01, the data are calculated as excess reserves minus total borrowings plus extended borrowings. From 2003-01-01 till 2007-11-01, the observations reflect excess reserves minus total borrowings plus secondary borrowings. From 2007-12-01, the definition changes to excess reserves minus discount window borrowings plus secondary borrowings. Please, check the latest definition of the discount window borrowings at https://fred.stlouisfed.org/series/DISCBORR.
This series has been discontinued with a phase of the simplification of reserves administration (https://federalregister.gov/a/2012-8562).
Board of Governors of the Federal Reserve System (US), Net Free or Borrowed Reserves of Depository Institutions (DISCONTINUED) [NFORBRES], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/NFORBRES, May 26, 2019.