COFIX (Cost of Funds Index)
It's the wholesale 'cost report card' showing what banks actually paid to stock up on money before lending it to you.
Definition COFIX (Cost of Funds Index) is a benchmark index that calculates the weighted average cost major commercial banks pay to secure funds for lending. It serves as the standard benchmark rate for adjustable-rate mortgages in South Korea.
Banks Buy Money at Wholesale Too
When a grocer buys apples at a higher wholesale price, retail apple prices go up. Banks work the exact same way. Banks do not just lend out money sitting idle in their own vaultsโthey 'buy' money from the outside world through customer deposits and bonds.
The interest a bank promises to pay to get this money is essentially its 'wholesale cost.' This includes interest paid on fixed-term deposits, installment savings, and bank debentures. Averaging all these borrowing costs each month gives us the Cost of Funds Index (COFIX).
Just as product prices climb when raw materials get expensive, loan interest rates rise when COFIX goes up. Conversely, if banks gather plenty of funds at low interest rates, COFIX drops, easing the interest burden on borrowers.
New vs. Outstanding Balance: What's the Difference?
When checking COFIX rates in the news or at a bank branch, you will often see two distinct types: 'New Handling Amount' and 'Outstanding Balance.' The difference lies in the time frame and calculation method.
The New Handling Amount COFIX calculates the average cost of funds newly secured over the past single month. When market interest rates fluctuate rapidly, this index reflects those changes immediately. If interest rates are plunging, choosing a loan tied to this rate can save you money faster.
On the other hand, the Outstanding Balance COFIX considers the average cost of all total funds currently held by the banks. Because it blends older, cheaper funds with newer, pricier funds, the index moves very gently even during market turbulence. If you prefer steady, predictable payments during volatile times, the Outstanding Balance index is usually a better fit.
To Be Exact: How Your Actual Loan Rate Is Set
Many people assume their mortgage interest rate will simply match the COFIX rate. To be more precise, the actual rate you pay is determined by adding the bank's profit margin and your individual credit risk to COFIX.
The basic formula is: 'Final Loan Rate = COFIX (Benchmark Rate) + Spread (Add-on Rate) - Preferential Discounts.' Here, COFIX acts as the base wholesale cost applied to everyone. On top of that, an add-on spread based on personal credit scores and bank operating costs is added. Reductions for salary direct deposits or card usage are then subtracted as preferential discount rates.
Ultimately, even if COFIX drops, your monthly interest payment might not decrease much if the bank raises its spread. When shopping for a home loan, you should look beyond monthly COFIX trends and carefully compare the spreads and discount conditions offered by each bank.
๐ค Common misconceptions
COFIX is a benchmark policy rate set directly by the central bank at monetary policy meetings.
Unlike the central bank's policy rate, COFIX is a market-driven index calculated and published around the 15th of each month by the Korea Federation of Banks, reflecting the actual borrowing costs of major commercial banks.
๐งบ Where you meet it
COFIX is the average wholesale cost banks pay to borrow money, serving as the starting benchmark for adjustable-rate mortgage loans.