Currency in circulation includes paper currency and coin held both by the public and in the vaults of depository institutions. The total includes Treasury estimates of coins outstanding and Treasury paper currency outstanding. This definition of currency in circulation differs from the currency component of the money stock, (http://research.stlouisfed.org/fred2/series/CURRENCY), which excludes currency held in vaults of depository institutions.
Effective February 2, 1984, reserve computation and maintenance periods have been changed from weekly to bi-weekly. Series with data prior to February 2, 1984 have different values reported from one week to the next. After February 2, 1984, the value repeats for 2 consecutive weeks.
Board of Governors of the Federal Reserve System (US), Monetary Base; Currency In Circulation [MBCURRCIRW], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/MBCURRCIRW/, October 6, 2015.