" Currently, the marginal reserve requirement equals 10 percent of a bank's demand and checking deposits. Banks can meet this requirement with vault cash and with balances in their Federal Reserve accounts. Neither of these assets earns interest, however, so banks have an incentive to minimize their holdings. Since the beginning of the last decade, required reserve balances have fallen dramatically. The decline stems in part from regulatory action: the Federal Reserve eliminated reserve requirements on large time deposits in 1990 and lowered the requirements on transaction accounts in 1992. But a far more important source of the decline in required reserves has been the growth of sweep accounts (chart). In the most common form of sweeping, funds in bank customers' retail checking accounts are shifted overnight into savings accounts exempt from reserve requirements and then returned to customers' checking accounts the next business day. Largely as a result of this practice, today only 30 percent of banks are bound by a reserve balance requirement (chart)."