Reserves that must be held against customer deposits of banks and other depository institutions. The reserve requirement ratio affects the expansion of deposits that can be supported by each additional dollar of reserves. The Board of Governors sets reserve requirements within limits specified by law for all depository institutions (including commercial banks, savings banks, savings and loan associations, credit unions, some industrial loan banks, and US agencies and branches of foreign banks) that have transaction accounts or nonpersonal time deposits. A lower reserve requirement allows more deposit and loan expansion and a higher reserve ratio permits less expansion.