The Corporate Bond Market and How It Trades

A large public company might have one stock and thirty different bonds outstanding, issued over a decade with different maturities, coupons, and covenants. That single fact explains most of what's unusual about how corporate bonds trade. There is no central limit order book aggregating buyers and sellers of "Apple debt" the way there is for Apple stock — there are thirty separate, thinly traded instruments, and each one might change hands only a few times on a typical day.

Why fragmentation forces a dealer market

An exchange order book works when many participants want to trade the same instrument frequently enough that resting limit orders reliably find a match. A single corporate bond issue, even from a large, liquid issuer, might trade only a handful of times a day — nowhere near enough volume to support a continuous order book. Dealers solve this by holding an inventory of bonds and standing ready to buy or sell at a quoted spread, effectively insuring customers against the risk of not finding a counterparty exactly when they want to trade, in exchange for that spread as compensation.

Pricing: spread to a benchmark, not price in isolation

Corporate bonds are quoted less often as a flat price and more often as a spread over a benchmark Treasury of similar maturity — the extra yield a buyer demands for taking on credit risk (and generally lower liquidity) versus a risk-free government bond. A bond might be quoted at "Treasury + 150," meaning its yield sits 150 basis points above the matched-maturity Treasury yield.

Worked example: converting spread to price

A 10-year corporate bond has a 5.00 percent coupon and is quoted at a spread of 180 basis points over the 10-year Treasury, which currently yields 4.20 percent. The bond's yield to maturity is therefore $4.20\% + 1.80\% = 6.00\%$.

Using a simplified annual-pay approximation for a 10-year, $1,000 face bond with a 5 percent coupon ($50/year) discounted at 6 percent:

$$P \approx \sum_{t=1}^{10} \frac{50}{(1.06)^t} + \frac{1000}{(1.06)^{10}} \approx 368 + 558 = 926$$

So the bond prices at roughly 92.6, or $926 per $1,000 face — trading at a discount because its coupon (5 percent) is below the yield the market demands (6 percent). If the spread widens by 50 basis points to 230 (yield rises to 6.50 percent), recomputing at 6.5 percent gives a price closer to 892 — an approximate 3.4-point drop for a 50-basis-point spread widening, illustrating how spread duration converts credit-spread moves directly into price moves, the same mechanic as Bond Duration and Convexity applied to the credit-spread component of yield rather than the rate component.

Worked example: reading TRACE for liquidity

Suppose a desk checks TRACE (the public post-trade reporting system for US corporate bonds) for a specific issue and sees only four trades reported that day, in sizes of $500,000, $2 million, $250,000, and $1 million, at prices ranging from 98.75 to 99.10 — a 35-cent spread across the day with no obvious trend. Compare that to the issuer's stock, which might see hundreds of thousands of trades cross in the same period at a bid-ask spread of a cent or two. That gap in trade count and spread width is not a coincidence of this particular bond; it is structural to how the whole asset class trades, because of fragmentation across issues and reliance on dealer capital rather than continuous matching.

Where you meet it in practice

Anyone pricing credit risk, running a credit portfolio, or building execution cost models for fixed income needs to internalize that "the corporate bond market" is really thousands of separate, thinly traded instruments held together by dealer capital and spread-to-benchmark quoting conventions — a structurally different liquidity profile from equities that shapes everything from transaction cost estimates to how credit spreads behave in a sell-off.