Sonia

SONIA (Sterling Overnight Index Average) is a benchmark interest rate for sterling-denominated derivatives and financial contracts. It represents the average interest rate that banks pay to borrow unsecured overnight funds in the sterling market.
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Updated on Jun 6, 2024
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3 key takeaways

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  • SONIA is a key interest rate benchmark for sterling-denominated financial instruments, used to calculate interest on swaps, futures, and other financial contracts.
  • It is based on actual transactions and reflects the average rate paid on overnight unsecured sterling transactions.
  • SONIA has become increasingly important as a replacement for LIBOR (London Interbank Offered Rate) in the sterling market.

What is SONIA?

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SONIA is the Sterling Overnight Index Average, an interest rate benchmark for the overnight funding market in the UK. Administered by the Bank of England, it reflects the average of interest rates paid on overnight unsecured borrowing by banks in the sterling market. SONIA is calculated based on actual transaction data, making it a reliable indicator of borrowing costs.

How SONIA is calculated

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SONIA is calculated using data from transactions that occurred in the overnight sterling money market. The calculation process involves the following steps:

  1. Data collection: The Bank of England collects transaction data from banks and financial institutions.
  2. Filtering transactions: Only eligible transactions that meet specific criteria, such as size and counterparty type, are included in the calculation.
  3. Averaging rates: The weighted average rate of these transactions is computed, excluding the highest and lowest values to reduce the impact of outliers.

Importance of SONIA

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SONIA serves as a critical benchmark for the financial markets:

  • Reliability: As it is based on actual transactions, SONIA provides a transparent and reliable measure of overnight funding costs.
  • Reform of interest rate benchmarks: With the phase-out of LIBOR, SONIA has become the preferred benchmark for sterling-denominated financial contracts. This transition enhances the stability and integrity of financial markets.
  • Widespread use: SONIA is used to calculate interest payments on a wide range of financial products, including swaps, futures, and bonds, making it a fundamental component of the sterling financial system.

Applications of SONIA

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SONIA is used in various financial instruments and contracts:

  • Interest rate swaps: SONIA is a common reference rate for floating leg payments in sterling-denominated interest rate swaps.
  • Floating rate notes (FRNs): These bonds pay interest based on a floating rate that often uses SONIA as the benchmark.
  • Overnight indexed swaps (OIS): SONIA is used as the reference rate in OIS contracts, which involve exchanging fixed interest payments for floating-rate payments based on SONIA.
  • Derivatives and futures: SONIA is widely used in the pricing and settlement of sterling-denominated derivatives and futures contracts.

SONIA vs. LIBOR

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SONIA differs from LIBOR in several key ways:

  • Basis of calculation: SONIA is based on actual overnight transactions, while LIBOR was based on estimated rates submitted by banks, which made it susceptible to manipulation.
  • Scope: LIBOR covered multiple tenors (overnight, one week, one month, etc.), whereas SONIA is a single overnight rate.
  • Transition: The shift from LIBOR to SONIA represents a move towards more transparent and robust benchmark rates in the financial industry.

Transition to SONIA

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The transition from LIBOR to SONIA involves several key steps:

  • Raising awareness: Financial institutions and market participants are informed about the transition and its implications.
  • Developing new products: Financial products previously linked to LIBOR are restructured to use SONIA as the reference rate.
  • Updating contracts: Existing contracts referencing LIBOR are amended to transition to SONIA, ensuring continuity and compliance with new benchmark standards.

SONIA has become a crucial benchmark for the sterling financial market, providing a reliable and transparent measure of overnight borrowing costs. As the financial industry continues to move away from LIBOR, SONIA’s role is expected to grow, further enhancing the integrity and stability of interest rate benchmarks.

For further exploration, you might look into related topics such as benchmark interest rates, interest rate swaps, and the LIBOR transition process.


Sources & references

Arti

Arti

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Arti is a specialized AI Financial Assistant at Invezz, created to support the editorial team. He leverages both AI and the Invezz.com knowledge base, understands over 100,000 Invezz related data points, has read every piece of research, news and guidance we\'ve ever produced, and is trained to never make up new...