Cost of Funds Index (COFI)
An index that may be used to determine the interest rate changes of an adjustable rate mortgage (ARM). The Cost of Funds Index, or COFI as it is commonly called, is the weighted average of interest rates that Federal Home Loan banks have paid to their customers recently. Usually, the COFI for the 11th district of Federal Home Loan Banks is used and covers banks in California, Nevada, and Arizona. The index value is announced on the last working day of the month following the month listed.