2.6 LIBOR and other benchmark rates

History of LIBOR

LIBOR (London Interbank Offered Rate) was the most widely referenced interest rate benchmark in the world for decades, underpinning an estimated $300+ trillion in financial contracts at its peak. Understanding its origins, how it worked, and why it's being replaced is essential for grasping how benchmark rates function in financial mathematics.

Origins and development

LIBOR's story starts in 1969, when Greek banker Minos Zombanakis needed a way to price an $80 million syndicated loan to Iran. He polled a group of reference banks for their borrowing costs and averaged the results. This ad hoc approach worked well enough that it became standard practice.

• The British Bankers' Association (BBA) formalized the process in 1986, creating an official daily reference rate for syndicated loans
• Initially covered three currencies (USD, GBP, JPY), then expanded over time to cover five currencies and seven tenors
• Gained widespread adoption because of its simplicity and its perceived reliability in reflecting actual interbank borrowing conditions

Role in financial markets

LIBOR served as the primary short-term interest rate benchmark globally. It was embedded in:

• Consumer lending: adjustable-rate mortgages, student loans, credit cards
• Corporate lending: syndicated loans, revolving credit facilities
• Derivatives: interest rate swaps, futures, forward rate agreements
• Fixed income: floating-rate notes, asset-backed securities

Its reach was so broad that even small movements in LIBOR rippled through the entire financial system.

LIBOR Calculation Methodology

LIBOR rates were determined through a daily survey of a panel of major banks. The goal was to produce a rate that reflected actual borrowing costs in the unsecured interbank market.

Panel bank submissions

1. A select group of banks (typically 11–18, depending on the currency) was chosen based on market activity and reputation
2. Each bank submitted the rate at which it believed it could borrow funds "in reasonable market size" for each currency and tenor
3. Submissions were due by 11:00 AM London time each business day
4. Banks were required to have internal processes ensuring the accuracy and integrity of their submissions

A critical weakness here: submissions were based on estimates, not necessarily on actual transactions. This distinction became central to the scandal later.

Trimmed average approach

1. Collect all panel bank submissions for a given currency and tenor
2. Remove the highest 25% and lowest 25% of submissions
3. Average the remaining middle 50% to produce the official LIBOR fixing
4. ICE Benchmark Administration (IBA) published the final rates around 11:55 AM London time

The trimming was designed to reduce the influence of outliers and make manipulation harder. In practice, it wasn't enough.

Types of LIBOR Rates

LIBOR wasn't a single number. It was a matrix of rates across multiple currencies and maturities, allowing precise pricing for different instruments.

Currency-specific LIBOR

• USD LIBOR: the most widely used globally, referenced in international transactions far beyond U.S. borders
• GBP LIBOR: used primarily for sterling-denominated contracts in UK markets
• EUR LIBOR: less common because the Eurozone relied more heavily on EURIBOR
• JPY LIBOR: important for yen-denominated loans and derivatives
• CHF LIBOR: used in Swiss franc financial products

By the end, only USD and GBP LIBOR remained active through the final cessation dates.

Tenor variations

• Overnight: shortest borrowing period, used for very short-term transactions
• 1-week and 1-month: commonly used for adjustable-rate mortgages and consumer loans
• 3-month: the most frequently referenced tenor, especially in derivatives markets
• 6-month and 12-month: applied to longer-term loans and floating-rate notes

The choice of tenor depends on the financial product's payment frequency and duration. A quarterly-reset floating-rate note, for example, would typically reference 3-month LIBOR.

LIBOR Applications

Loan pricing

Floating-rate loans are typically priced as LIBOR plus a credit spread that reflects the borrower's risk. For example, a corporate borrower might pay 3-month LIBOR + 150 basis points (1.50%).

• Syndicated loans use LIBOR to ensure consistent pricing across multiple lenders
• Consumer products (mortgages, student loans) often use LIBOR as the base rate
• Corporate credit facilities tie interest rates to LIBOR plus a margin based on creditworthiness

Derivative contracts

• Interest rate swaps use LIBOR as the floating leg reference rate. One party pays fixed, the other pays LIBOR
• Forward rate agreements (FRAs) settle based on the difference between the agreed rate and the LIBOR fixing
• Eurodollar futures are based on 3-month LIBOR and are among the most liquid futures contracts in the world
• Options on LIBOR-based instruments allow participants to hedge volatility and directional exposure

Bond markets

• Floating-rate notes (FRNs) pay coupons equal to LIBOR plus a fixed spread
• Asset-backed securities (ABS) and mortgage-backed securities (MBS) often incorporate LIBOR in their payment waterfalls
• LIBOR also serves as a benchmark for relative value analysis when pricing fixed-income securities

LIBOR Manipulation Scandal

The LIBOR scandal is one of the largest financial frauds in history. It revealed that the rate underpinning hundreds of trillions of dollars in contracts was being systematically manipulated.

Regulatory investigations

Concerns about LIBOR's integrity surfaced during the 2008 financial crisis, when reported LIBOR rates seemed suspiciously low given the stress in interbank markets. Banks had incentives to underreport their borrowing costs to appear healthier than they were.

• The U.S. Commodity Futures Trading Commission (CFTC) launched formal inquiries in 2010
• Multiple regulators (FSA, DOJ, SEC, and others) conducted parallel investigations across jurisdictions
• Evidence included electronic communications showing traders colluding with rate submitters to move LIBOR in directions that benefited their trading positions
• The manipulation was systematic, involving multiple banks over several years

Market impact

• Fines: banks paid billions in penalties. Barclays alone paid $453 million in 2012; UBS paid $1.5 billion
• Legal actions: municipalities, pension funds, and investors who held LIBOR-linked contracts filed lawsuits alleging losses from manipulated rates
• Reputational damage: the scandal undermined trust not just in LIBOR but in benchmark-setting processes generally
• Regulatory reform: the scandal accelerated calls for transaction-based benchmarks that would be harder to manipulate

LIBOR Transition

Reasons for replacement

The manipulation scandal was the catalyst, but several structural problems also drove the transition:

• Declining transaction volume: actual unsecured interbank lending had shrunk dramatically, meaning LIBOR submissions were increasingly based on "expert judgment" rather than real trades
• Credibility loss: market participants no longer trusted the rate
• Regulatory push: authorities wanted benchmarks anchored in observable transactions, not bank estimates
• Systemic risk: overreliance on a single benchmark created concentration risk for the entire financial system

Timeline and milestones

• 2017: UK Financial Conduct Authority (FCA) announces LIBOR will not be sustained beyond end of 2021
• 2019: Alternative reference rates identified; working groups established in major jurisdictions
• 2020: Major central counterparties (CCPs) switch to SOFR discounting for USD interest rate products
• 2021: Most new USD LIBOR contracts cease, with limited exceptions
• June 2023: Final USD LIBOR settings published, marking the definitive end of LIBOR

Alternative Reference Rates

The replacement rates share a common design philosophy: they're based on actual overnight transactions in deep, liquid markets, making them far more resistant to manipulation.

SOFR vs LIBOR

SOFR (Secured Overnight Financing Rate) is the preferred replacement for USD LIBOR. Key differences:

The secured vs. unsecured distinction matters: SOFR will generally be lower than LIBOR because it doesn't include a bank credit risk premium. This difference is addressed through credit adjustment spreads during the transition.

SONIA and €STR

• SONIA (Sterling Overnight Index Average) replaced GBP LIBOR. Reformed in 2018, it's based on actual overnight unsecured transactions in sterling markets
• €STR (Euro Short-Term Rate) replaced EUR LIBOR and EONIA in the Eurozone. It reflects wholesale euro unsecured overnight borrowing costs of euro area banks

Other regional benchmarks

• TONAR (Tokyo Overnight Average Rate): replaces JPY LIBOR
• SARON (Swiss Average Rate Overnight): replaces CHF LIBOR; notably, this is a secured rate like SOFR
• CORRA (Canadian Overnight Repo Rate Average): the CAD benchmark
• AONIA (AUD Overnight Index Average): replaces AUD LIBOR

Challenges in Benchmark Transition

Legacy contracts

The sheer volume of existing LIBOR-linked contracts created enormous transition challenges:

• Many contracts extended well beyond the LIBOR cessation date, some out to 2050 or later
• "Tough legacy" contracts lacked adequate fallback provisions and were difficult or impossible to amend (e.g., bonds requiring unanimous bondholder consent)
• Legislative solutions were needed: the U.S. passed the LIBOR Act (2022), and the UK FCA authorized "synthetic LIBOR" as a temporary bridge for certain contracts
• Value transfer risk: switching from LIBOR to an alternative rate could create winners and losers if the spread adjustment doesn't perfectly offset the difference

Operational adjustments

• Systems and infrastructure needed updates to handle new rate conventions (e.g., compounding in arrears vs. term rates)
• Risk management models and valuation methodologies required recalibration
• Documentation, disclosures, and client communications all needed revision
• Counterparties had to coordinate on renegotiating and amending existing contracts

Risk Management Considerations

Basis risk

When LIBOR and its replacement rates don't move in lockstep, basis risk arises. This is a significant concern because:

• LIBOR includes a bank credit risk premium; SOFR does not. During credit stress, this gap widens
• Alternative rates can behave differently during market dislocations (SOFR spiked during the September 2019 repo market stress)
• Hedging strategies that worked under LIBOR may not translate directly to the new rates
• New instruments like basis swaps (e.g., SOFR vs. term SOFR, or SOFR vs. a credit-sensitive rate) have developed to manage this risk

Fallback provisions

Robust fallback language in contracts is the first line of defense against LIBOR cessation disruption:

• ISDA's fallback protocol for derivatives provides a standardized approach: if LIBOR ceases, contracts automatically switch to the alternative rate plus a fixed spread adjustment
• Fallback provisions typically follow a waterfall structure: try the preferred replacement rate first, then a series of alternatives
• Trigger events that activate fallbacks include permanent cessation of LIBOR and pre-cessation triggers (when LIBOR is declared non-representative)
• Disputes over fallback interpretation remain a litigation risk, particularly for contracts with ambiguous language

Regulatory Framework

Benchmark regulation

Several regulatory frameworks now govern how benchmarks are set and administered:

• EU Benchmark Regulation (BMR), introduced in 2018, requires enhanced governance, transparency, and accountability for benchmark administrators
• UK Benchmark Regulation mirrors the EU BMR post-Brexit
• IOSCO Principles for Financial Benchmarks provide global standards that most jurisdictions reference
• The Dodd-Frank Act in the U.S. grants authority to regulate benchmark-setting processes

Compliance requirements

• Benchmark administrators must maintain enhanced governance structures
• Contributing banks follow mandatory codes of conduct for submissions
• Regular external audits assess calculation methodologies
• Increased disclosure requirements cover benchmark composition and methodology
• Stringent record-keeping standards apply to all aspects of benchmark administration

Future of Benchmark Rates

Market adoption trends

• Liquidity in SOFR-based derivatives and cash products has grown rapidly since 2021
• Term rate structures for overnight rates (like CME Term SOFR) are now available, though regulators prefer compounded-in-arrears calculations for most products
• Credit-sensitive rates like AMERIBOR and Bloomberg Short-Term Bank Yield Index (BSBY) emerged as complements to risk-free rates, though BSBY was discontinued in 2024, highlighting the difficulty of creating durable new benchmarks
• Regional adoption varies: some jurisdictions have transitioned faster than others

Potential innovations

• Exploration of blockchain and distributed ledger technology for more transparent benchmark calculation and distribution
• Integration of machine learning in rate-setting and anomaly detection processes
• Development of multi-rate environments where different products reference different benchmarks depending on their risk characteristics
• Ongoing research into methodologies that better capture bank funding costs while remaining anchored in actual transactions