Some loans or investments are preferred to others even where there is the same element of risk involved. A railroad bond, for example, usually bears a lower rate of interest than a first-class farm mortgage. Here the risk element is very low, but bonds are much easier sold than are mortgages; hence the difference in rates. Banks also vary rates of interest paid on deposits according to the degree of fixity. City banks often pay 2 per cent on checking deposits and 3 per cent on savings. Depositors may withdraw the former on demand, while in the latter case the bank has the right to compel formal notice of several days. Likewise in lending money, banks usually charge less interest on a call loan than on a time loan. One they can have paid on demand; for the other they must wait until it is due. Thus we see that the lender. who reserves the right to have his loan returned to him quickly must accept a less reward for his waiting than would be necessary if he were willing to forego this reservation. Also the borrower is unwilling to pay as much premium for capital over which he has an uncertain control as he would pay if his control were made more certain.