IBOR stands for Interbank Offered Rate, a family of benchmark interest rates that once anchored the pricing of roughly $400 trillion in financial contracts worldwide. The best-known member was the London Interbank Offered Rate, or LIBOR. Others covered the euro, yen, Swiss franc, and other currencies. Each was meant to reflect the interest rate at which large banks would lend to one another without collateral. Regulators have since dismantled the system after finding that banks manipulated the submissions and that the underlying lending market had largely dried up. Transaction-based overnight rates now do the same job with far less room for abuse.
What an Interbank Offered Rate Measured
An IBOR represented the rate at which major banks said they could borrow unsecured funds from other banks for a set period. The word “unsecured” carried most of the weight. No collateral backed these loans, so the quoted rate had to price in the risk that the borrowing bank might default. When confidence in the banking system dropped, IBORs climbed. When it returned, they fell.
The rates were also forward-looking. A three-month LIBOR quote projected borrowing costs over the next 90 days rather than recording what had already happened. That combination — forward-looking and credit-sensitive — made IBORs useful for pricing instruments like interest rate swaps and term loans, where both parties needed a shared view of future funding costs.
LIBOR was published in multiple currencies and maturities. Rates covered the U.S. dollar, British pound, euro, Japanese yen, and Swiss franc, with tenors from overnight to twelve months. Three-month U.S. dollar LIBOR was, for decades, the single most referenced number in global finance. It reached far beyond trading desks. Adjustable-rate mortgages, private student loans, corporate credit facilities, auto loans, and credit card agreements all used LIBOR as their floating reference. A homeowner in Ohio and a multinational in London were, in effect, both paying interest based on the same panel of bank estimates.
How LIBOR Was Set Each Morning
Every London business morning, a panel of major global banks answered a deceptively simple question: at what rate could you borrow unsecured funds from another bank? Each submission was an estimate, not a report of an executed trade. The ICE Benchmark Administration collected the answers and threw out the highest and lowest quartiles. If 16 banks submitted, the top four and bottom four were discarded, and the published LIBOR was the simple average of the remaining eight.1Bank for International Settlements. LIBOR and “Benchmark Tipping”: Then and Now
Trimming was supposed to stop any single bank from dragging the number in its favor. In theory, it worked. In practice, when the underlying lending market shrank and submissions became closer to guesswork, even the trimmed average could be steered by a handful of coordinated submitters.
Why IBORs Were Retired
The Market Behind the Rate Disappeared
LIBOR was designed to capture the cost of unsecured term lending between banks. After the 2008 financial crisis, banks largely stopped lending to each other on those terms. They moved to secured, collateralized borrowing or relied on central bank facilities. As real unsecured interbank loans collapsed in volume, the panel banks had fewer transactions to anchor their daily submissions. A market-derived rate slowly turned into an exercise in expert judgment.
In a July 2017 speech, Andrew Bailey, then chief executive of the UK Financial Conduct Authority, said the market LIBOR claimed to measure was “no longer sufficiently active,” and a rate sustained by judgment rather than trades carried an “inherently greater vulnerability to manipulation.” He announced that the FCA would no longer compel banks to submit LIBOR quotes after the end of 2021.2Financial Conduct Authority. The Future of LIBOR
The Manipulation Scandal
The vulnerability Bailey described was not hypothetical. Investigations by regulators in the U.S., UK, and Europe found that traders at major banks had been submitting false rates for years. Some inflated or deflated quotes to benefit derivatives positions. Others submitted artificially low rates during the financial crisis to make their banks appear healthier than they were. Regulators imposed billions in fines on institutions including Barclays and UBS, and several traders were criminally prosecuted in both U.S. and UK courts.3U.S. Department of Justice. Two Former Rabobank Traders Sentenced to Prison for Manipulating US Dollar and Japanese Yen LIBOR The scandal confirmed what the structural decline had already suggested: a benchmark built on voluntary, unverifiable estimates from the same banks that profited from the rate could not be salvaged.
What Replaced the IBORs
The successor rates are collectively called Risk-Free Rates, or RFRs. They differ from IBORs in almost every respect. RFRs are backward-looking rather than forward-looking. They are nearly free of bank credit risk. They are calculated from large pools of completed overnight transactions rather than from bank estimates. That transactional foundation is what makes them harder to manipulate.
Each major currency now has its own replacement:
- U.S. dollar: the Secured Overnight Financing Rate (SOFR), based on overnight Treasury repurchase agreement transactions. Daily trading volume regularly exceeds $3 trillion.4Federal Reserve Bank of St. Louis. Secured Overnight Financing Volume (SOFRVOL)
- British pound: the Sterling Overnight Index Average (SONIA), administered by the Bank of England.
- Euro: the Euro Short-Term Rate (€STR), published by the European Central Bank.
- Japanese yen: the Tokyo Overnight Average Rate (TONA), the uncollateralized overnight call rate in Japan.5Bank of Japan. Interest Rate Benchmark Reform
- Swiss franc: the Swiss Average Rate Overnight (SARON), based on the Swiss repo market.
Because these rates reflect collateralized or very short-term lending, they strip out the bank credit risk that was baked into LIBOR. Any credit premium can be added separately and transparently rather than buried inside the benchmark itself.
What Happened to Existing LIBOR Contracts
The representative panel-based LIBOR ceased publication on June 30, 2023. The FCA required a temporary “synthetic” version of some LIBOR settings to keep legacy contracts running, but that bridge was limited to existing deals and has now closed: the one-, three-, and six-month synthetic U.S. dollar LIBOR settings were published for the last time on September 30, 2024.6Financial Conduct Authority. Remaining Synthetic US Dollar LIBOR Settings – Less Than 1 Month to Go
For U.S. contracts that lacked workable fallback language, Congress stepped in with the Adjustable Interest Rate (LIBOR) Act, codified at 12 U.S.C. Chapter 55. The statute automatically replaces LIBOR with a Federal Reserve Board-selected SOFR-based rate, along with the appropriate tenor spread adjustment. Institutions that use the Board-selected replacement are protected by a broad safe harbor: the switch counts as “substantial performance” of any LIBOR-linked obligation, is not a breach of contract, does not give any party the right to terminate or suspend the agreement, and is not treated as an amendment.7Office of the Law Revision Counsel. 12 USC Chapter 55 – Adjustable Interest Rate (LIBOR)
Because LIBOR carried a bank credit premium and SOFR does not, a direct one-for-one swap would have changed the economics of every legacy contract. The Alternative Reference Rates Committee recommended a fixed Credit Spread Adjustment, calculated using the five-year historical median difference between LIBOR and SOFR for each tenor, added permanently to the replacement rate. The adjustment is meant to leave borrowers and lenders in roughly the same economic position after the switch.8Alternative Reference Rates Committee. ARRC Announces Recommendation of a Spread Adjustment Methodology for Cash Products
Consumer products got their own treatment. The Consumer Financial Protection Bureau updated Regulation Z to require specific notices before a LIBOR index changed on a consumer loan. For a home equity line of credit, the lender had to mail a change-in-terms notice at least 15 days before the new rate took effect. For open-end credit like credit cards, the required lead time was 45 days. In both cases, the notice had to disclose the replacement index and any adjusted margin used to calculate the new rate.9Federal Register. Facilitating the LIBOR Transition (Regulation Z)
For most borrowers, the transition itself was not meant to change monthly payments in any meaningful way; the credit spread adjustment was designed to keep the economics steady. What changes going forward is the benchmark’s behavior. Because SOFR tracks overnight Treasury repo rates rather than unsecured bank lending, it tends to be less volatile during banking-sector stress. Whether that helps or hurts a given borrower depends on which way rates move next, but the underlying number is harder to game than the one it replaced.