The Federal Home Loan Bank of San Francisco reported that the monthly cost-of-funds index for July was 9.365%. The index for June was 9.565%. Changes in interest rates on adjustable-rate mortgages offered by many savings institutions and commercial banks are tied to changes in the index. The cost-of-funds index reflects the interest rates paid by savings institutions in Arizona, California and Nevada on their various sources of mortgage money. The index is announced on or near the last working Friday of each month for the previous month.