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SOFR: A comprehensive guide


How SOFR, the benchmark rate chosen to replace USD LIBOR, works and what drives its movements

Why was SOFR created?

In July 2017, the UK Financial Conduct Authority (FCA) announced that it would no longer require banks to submit cost of funds quotes in support of calculating LIBOR, calling into question LIBOR’s viability and availability past 2021. In June 2017, the Alternative Reference Rates Committee (ARRC), a private-public partnership convened by the Federal Reserve Board of Governors (the Fed) and the Federal Reserve Bank of New York (the New York Fed), identified the Secured Overnight Financing Rate (SOFR) as its preferred replacement for USD LIBOR.

What is SOFR?

Unlike USD LIBOR, SOFR is a fully transaction-based rate, and therefore, less susceptible to market manipulation and more attractive to regulators. SOFR measures of the cost of borrowing cash overnight collateralized by Treasury securities. There are approximately $900 billion of actual market transactions supporting the daily calculation of SOFR. Conversely, USD LIBOR relies primarily on expert judgment of the LIBOR panel’s submissions to calculate this rate. The most actively traded USD LIBOR tenor is three months, and less than $1 billion of transactions typically support the calculation of this rate each business day, particularly in the current COVID-19 environment. There is a much more robust market supporting the calculation of SOFR.

How is SOFR calculated?

The New York Fed calculates SOFR by taking the volume-weighted median (50th percentile) of transactions in three markets for repurchase (repo) agreements collateralized by U.S. Treasury securities:

  1. Tri-party repo data
  2. General Collateral Finance (GCF) repurchase agreements transaction data
  3. Bilateral Treasury repo transactions cleared through FICC’s DVP Service (Fixed Income Clearing Corporation’s Delivery vs. Payment Service).

The New York Fed publishes SOFR at 8 a.m. EST each day. In contrast to the different term LIBORs (i.e., 1-month LIBOR, 3-month LIBOR, etc.), it is an overnight, fully secured rate.

Why did the ARRC identify SOFR, as compared with other alternatives, as the replacement for USD LIBOR?

The ARRC’s primary stated criteria in choosing a replacement rate for USD LIBOR included liquidity and robustness of underlying markets, as well as not restricting the Fed’s future monetary policy choices. Based on these and other criteria, the ARRC identified SOFR, where disinterested third-party clearinghouses report the terms of the large volume of transactions underlying the rate, as compared with determining LIBOR, which, as a practical matter, is based on panel banks’ submitting borrowing costs based on expert judgment because there is so little unsecured bank-to-bank lending post-Great Financial Crisis. In identifying SOFR, the ARRC ruled out the use of certain other rates, including the Effective Federal Funds Rate, citing market size and the potential to constrain monetary policy, as well as Treasury bill or bond rates, citing concerns around certain technical factors and how they respond to safe haven demands in periods of stress.

What are the repo markets that underlie SOFR?

Repo markets, broadly, are those in which banks and other large financial institutions and corporates borrow or lend cash secured by liquid securities, often U.S. Treasuries, for short periods of time, typically overnight. In the tri-party repo market, a clearing bank sits between broker/dealers that borrow from cash investors (e.g., money market funds, mutual funds, et al.). The GCF repo market is a tri-party repo market used only between dealers who borrow cash against general collateral (i.e., securities that are not specified until the end of the trading day). In the DVP repo market, asset managers and other investors (e.g., REITs) borrow specific securities from broker-dealers and securities lenders on a bilateral or cleared basis.

What drives supply and demand in the repo markets that underlie SOFR?

Some of the factors that impact supply and demand in the Treasury repo market are:

  • Fed Funds Target Rate: The lowest U.S. rate is the rate paid by the Fed to investors in certain repo transactions. This rate is the lower bound of the Fed Funds target range; increases in the Fed Funds target range will drive an increase in repo rates. This is the most significant driver of SOFR and sets a floor below which SOFR is unlikely to fall.
  • Reduced bank balance sheet availability: Bank balance sheets typically experience greater pressure at quarter end and year end; these liquidity and capital needs are often funded through repo, which increases repo rates. This factor drives the tendency of SOFR to spike at quarter- and year-end.
  • MMF sensitivity to T-Bill Issuance: Money market funds (MMF) account for about half of the repo market activity from which SOFR is calculated. MMFs can typically invest in repo, Treasury Bills, and discount notes. An increase in T-Bill issuance will push yields higher, causing MMFs to substitute bills for repo assets, driving an increase in repo rates.
  • Government MMF balance increase: Higher balances in government MMFs result in more cash available for repo, which lowers repo rates.
  • Flight to safety/quality: Periods of market stress in “risk assets” including equities, corporate bonds, real estate, et. al. increase demand for Treasury repo collateral, pushing repo rates down.

Isn’t a market-driven rate inherently volatile?

The market dynamics of the Treasury repo market make daily spot SOFR more volatile than spot USD LIBOR. To address this, the ARRC, the International Swaps and Derivatives Association (ISDA), and other market participants have recommended a variety of options, all of which reduce the volatility otherwise associated with a daily rate, for calculating SOFR over a given interest period.

  • Simple daily SOFR in arrears: simple average of daily SOFR during an interest period, determined at the end of the period
  • SOFR compounded in arrears: compounded daily SOFR during an interest period, determined at the end of the period
  • SOFR compounded in advance: compounded rate based on daily SOFR during the previous 30, 60, or 90 days, determined at the beginning of an interest period
  • Term SOFR: forward-looking rate determined by market expectations of future SOFR settings

What SOFR-related resources are available?

Speak to a Chatham expert

Please reach out to the Chatham team if you have questions around the USD LIBOR transition or how the use of SOFR in your loans and derivatives could impact your interest rate exposure.


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