Floating Rate Bond Mechanics

A floating rate bond has a coupon that resets every 3 or 6 months based on a reference rate (most commonly SOFR) plus a fixed spread, allowing the bond’s yield to rise or fall with prevailing interest rates and isolating the bondholder from duration risk.

How coupon resets work: SOFR plus spread

A floating-rate bond pays coupon = SOFR + 200 basis points. If SOFR is currently 5%, the bondholder receives 7% annually (100 basis points = 1%). Every six months, the coupon is recalculated: if SOFR falls to 4%, the coupon drops to 6%. This mechanism insulates the bondholder from interest rate risk—when rates rise, coupons rise, preventing bond prices from falling sharply. In a fixed-rate bond, rising rates mean the bond’s price falls (because new bonds with higher coupons now compete). Floating-rate bonds avoid this—their coupons simply adjust upward, keeping prices near par (face value).

Reference rate evolution: LIBOR to SOFR transition

For decades, LIBOR (London Interbank Offered Rate) was the benchmark. Banks self-reported the cost of borrowing; the reported rates were averaged to compute LIBOR. However, LIBOR was easily manipulated (wide discretion in reporting), and a 2012 scandal revealed widespread rate-fixing. Regulators demanded a shift to transaction-based rates. The SOFR (Secured Overnight Financing Rate), launched in 2018, is calculated from actual repurchase agreements (repo transactions), making it manipulation-proof. The US Treasury and Fed mandated SOFR for new floating-rate debt; old LIBOR contracts were “tough legacy” (still in use but slated for phase-out by 2024 in most markets). Many floating-rate notes issued before 2020 used LIBOR; these are gradually maturing or being refinanced at SOFR.

Spread mechanics and credit risk

The spread (the fixed percentage above the reference rate) reflects issuer credit quality. A AAA-rated bond might trade at SOFR + 50 basis points; a BBB-rated bond at SOFR + 200 basis points. This spread doesn’t reset—it’s locked at issuance and doesn’t change even if the issuer’s credit rating changes. This means a bond issued at SOFR + 50 bp could widen to SOFR + 150 bp in the secondary market if the issuer’s credit deteriorates. However, on the reset date, the coupon still uses the original 50 bp spread. This structure isolates the reference-rate reset from credit-spread risk—the coupon floats with rates, but the spread is fixed.

Price volatility and duration

A fixed-rate 10-year bond has a duration of ~8 years—a 1% rise in yields triggers an ~8% price decline. A floating-rate bond reset every 6 months has a duration of ~0.25 years (6 months ÷ 2)—the same 1% yield rise causes a ~0.25% price decline. This ultra-low duration makes floating-rate bonds nearly risk-free in terms of interest-rate moves. However, the trade-off is yield: because investors pay less for duration risk, floating-rate bonds offer lower coupons than fixed-rate bonds. A 10-year fixed-rate bond might yield 5%; a floating-rate bond might yield SOFR + 100 bp (currently ~6%, but only because SOFR is elevated).

Negative convexity and cap features

Some floating-rate bonds have caps (maximum coupon) and floors (minimum coupon). A bond paying SOFR + 200 bp with a 7% cap means the coupon never exceeds 7%, even if SOFR + spread would suggest 10%. This benefits the issuer (capping liabilities in a high-rate environment) but hurts the bondholder (upside capped). Similarly, a floor ensures the coupon never falls below some level (e.g., 3%), protecting the bondholder in a low-rate scenario but limiting issuer upside. Bonds with caps have negative convexity—as rates rise beyond the cap, the bond behaves like a fixed-rate bond (price falls). This was a major issue during the 2022 rate hike: floating-rate corporate bonds with low caps underperformed because investors feared the capped coupons.

When floating-rate bonds outperform: rising-rate environments

In 2022–2024, when interest rates rose sharply, floating-rate bonds outperformed fixed-rate bonds. A bondholder holding a SOFR + 200 bp bond saw coupons jump from 3% to 7% as SOFR rose—capturing the full benefit of higher rates. A fixed-rate bondholder with a 3% coupon saw bond prices collapse. Floating-rate bonds are thus interest-rate hedges—ideal for investors who view rising rates as likely or who want to lock in current spread premiums while avoiding duration losses. This is why central banks hold floating-rate debt and why pension funds with inflation concerns favor them.

Basis risk: spread vs. rate moves

Floating-rate bonds are protected against reference rate changes but exposed to spread risk—the margin above the reference rate can widen or tighten based on credit conditions and market demand. During the 2008 financial crisis, spreads widened 500+ basis points for corporate floating-rate bonds, even as SOFR (then LIBOR) fell—a double whammy for investors (coupons fell, but bond prices fell further due to spread widening). This basis risk is the main danger with floating-rate debt. Low-credit-quality issuers’ floating-rate bonds are riskier than they appear; spreads can blow out rapidly.

Application in mortgages and adjustable-rate debt

Adjustable-rate mortgages (ARMs) are consumer-level floating-rate debt—the rate resets annually or every few years. A borrower locking in an ARM rate of SOFR + 250 bp enjoys lower initial rates than a 30-year fixed mortgage but faces rate-hike risk after the initial period. During 2022–2023, ARMs reset upward sharply, straining borrowers. This illustrates the distribution of interest-rate risk: the lender (mortgage servicer) is hedged by floating rates; the borrower bears the risk. Understanding this risk distribution is key to personal finance decisions.

Portfolio role and duration management

Floating-rate bonds serve as cash substitutes or duration hedges. A pension fund with a 5-year liability duration might hold 3-year fixed bonds + 2-year floating bonds to match. If rates rise, the floating bonds’ coupons rise, offsetting the interest-rate risk on the fixed bonds. Alternatively, institutions use floating-rate bonds to park excess cash while earning a spread premium over cash. Since SOFR rates now closely track Fed overnight rates, floating-rate bonds offer competitive short-term yields—typically 20–100 basis points above cash.