The 11th District Cost of Funds Index (COFI) is the weighted average of the cost of borrowings (funds) to member banking institutions of the Federal Home Loan Bank of San Francisco (the 11th District). The index rate tends to lag market interest rate adjustments and is relatively stable because institutions borrow money for varying terms and do not pay market rates for all of their funds. For example, institutions most commonly borrow from depositors in the form of certificates of deposit (cd's). The terms on cd's vary from several days to several years and the interest rates paid were determined at the time of the deposit.

This index is reported monthly. Although, the reported rate generally lags behind two months (e.g. January's index is reported in March, February's index is reported in April, etc.)