A savings bank differs materially from a commercial bank. First of all, a true savings bank is a mutual affair conducted primarily for the benefit of its depositors, though in some sections of the country stock savings banks may be found. In states where there are no savings banks, that function is performed by the various commercial banks. Savings banks usually receive deposits of one dollar and upward on which they pay interest, do not pay out money on checks drawn against deposits, and may require a formal notice of several days before deposits can be withdrawn. Unlike commercial banks, savings banks usually contract loans for a year or more. This they are able to do for two reasons. First, they seldom have extraordinary demands made on them by depositors; and second, their privilege to compel depositors to serve formal notice of withdrawal gives the opportunity to raise the required cash from the sale of mortgages, bonds, or other securities. Savings banks, by receiving small amounts and paying interest, encourage thrift; their aggregate deposits, exceeding five billion dollars, comprise an important source from which industry can draw capital.