11th District Cost of Funds Index is a benchmark-rate concept used in loan pricing, derivatives, valuation, or interest-rate analysis.
The 11th District Cost of Funds Index, commonly referred to as COFI, is a monthly weighted average interest rate calculated based on the interest expenses of savings institutions operating within the states of Arizona, California, and Nevada. This index is widely recognized in financial markets, particularly for its use in adjustable-rate mortgages (ARMs).
COFI is computed by the Federal Home Loan Bank of San Francisco (FHLBSF) and reflects the cost of funds for savings institutions within its 11th District. The calculation involves a weighted average of the interest rates paid by these institutions on various types of deposits, including:
The formula can be expressed as:
where:
COFI originated in the 1980s during a period of significant interest rate volatility. It was developed to provide a more stable and predictable benchmark for adjustable-rate mortgages (ARMs). This helped align the cost of funds for lenders with the interest rates charged to borrowers.
COFI is notably used as an index for ARMs, especially in the western United States. Lenders use COFI to determine interest rate adjustments for these loans. Because COFI represents a weighted average of interest rates, it tends to be less volatile than other indices like the London Interbank Offered Rate (LIBOR), providing more stability for borrowers.
Financial markets closely monitor COFI as it reflects the cost of borrowing for savings institutions. Changes in COFI can influence lending rates, the profitability of financial institutions, and broader economic conditions in the states of Arizona, California, and Nevada.
COFI is one of several indices used in mortgage lending. Key comparisons include:
The main distinction of COFI lies in its regional specificity and its relatively stable nature.
Use 11th District Cost of Funds Index as a decision signal when it changes allocation, benchmark fit, expected return, volatility, liquidity, fees, or tax drag. If portfolio weight, risk budget, rebalancing action, and downside exposure are unchanged, it is mostly a classification label.
Use 11th District Cost of Funds Index when economic context needs to become a finance assumption: interest rates, inflation, demand, exchange rates, commodity prices, credit conditions, fiscal capacity, or risk appetite. The practical value of 11th District Cost of Funds Index is turning a macro idea into a model input or investment constraint.
Review 11th District Cost of Funds Index by asking which forecast variable changes, which asset or borrower is exposed, and how quickly the effect passes through to cash flows, discount rates, margins, or funding costs. If 11th District Cost of Funds Index changes valuation, underwriting, hedging, budgeting, or portfolio positioning, document the assumption. If 11th District Cost of Funds Index is only background commentary, keep it separate from the base-case numbers.
Pull the source dataset, release calendar, revision history, policy statement, market pricing, and forecast bridge. For 11th District Cost of Funds Index, the useful evidence shows whether rates, inflation, demand, currency, credit conditions, or risk appetite changed a finance assumption.
For 11th District Cost of Funds Index, the decision impact is whether a forecast, discount rate, inflation case, currency assumption, demand view, credit outlook, or policy expectation changes. If no finance assumption changes, keep the economic idea outside the base-case model.
The analysis boundary for 11th District Cost of Funds Index is crossed when rates, inflation, demand, currency values, fiscal capacity, credit conditions, and risk appetite do not change a forecast or market assumption. Then keep it outside the base-case model.
Trace 11th District Cost of Funds Index from benchmark observation to reset date, spread, compounding rule, fallback language, discount curve, and contract cash flow. 11th District Cost of Funds Index matters when it changes borrower cost, lender return, derivative settlement, hedge effectiveness, or valuation of a floating-rate exposure.
The use boundary for 11th District Cost of Funds Index is reached when observation date, tenor, spread, compounding, fallback, curve input, hedge alignment, and contract cash flow are unchanged. In that case, treat the benchmark as reference data rather than a changed rate exposure.
The decision marker for 11th District Cost of Funds Index is the moment rate mechanics change: fixing, observation date, tenor, spread, compounding, fallback, curve input, hedge alignment, or contract cash flow. If those mechanics are unchanged, keep the benchmark as reference data.
The risk check for 11th District Cost of Funds Index is whether the rate input matches the contract mechanics. Test observation date, tenor, spread, compounding, fallback, holiday convention, curve source, and hedge alignment before changing cash-flow or valuation conclusions.
Decision evidence for 11th District Cost of Funds Index should show fixing source, observation date, tenor, spread, compounding convention, fallback clause, curve input, and hedge record. 11th District Cost of Funds Index can change analysis only when those facts alter cash flow, discounting, or hedge effectiveness.
Review evidence for 11th District Cost of Funds Index should make the benchmark-rate evidence traceable, not just definitional. For 11th District Cost of Funds Index, tie the evidence to the administrator publication, tenor, observation date, and rate source used in the calculation and explain why that evidence is reliable enough for the finance decision.
Before relying on 11th District Cost of Funds Index, document the decision context: the accrual period, reset date, fallback language, and compounding or averaging convention. Keep the 11th District Cost of Funds Index evidence trail visible: independent rate check, contract reference, and exception handling when the benchmark is unavailable. In Fixed Income work, 11th District Cost of Funds Index matters when it changes coupon accruals, discounting, hedge effectiveness, valuation, or borrower cost.
The practical risk for 11th District Cost of Funds Index is that rate references are fragile when the tenor, date, fallback, or compounding convention is undocumented. If those facts are unavailable, keep 11th District Cost of Funds Index in the explanatory layer instead of treating it as decision-grade evidence.
11th District Cost of Funds Index is material when it can change a finance conclusion, not just when 11th District Cost of Funds Index appears in a document. For 11th District Cost of Funds Index, test whether the evidence affects coupon accruals, discount rates, reset mechanics, fallback language, hedge testing, or borrower cost. If those decision points are unchanged, keep 11th District Cost of Funds Index explanatory and avoid overweighting it in the final decision.
A practical materiality check is to name the decision that would change if 11th District Cost of Funds Index is wrong, stale, missing, or tied to the wrong period. 11th District Cost of Funds Index warrants deeper review only when a different rate source, tenor, or observation date would change pricing, valuation, or contract cash flows.