The On-the-Run/Off-the-Run Treasury Spread

The US Treasury auctions new bonds of each maturity — say, a new 10-year note — roughly every few months. The freshest one is called on-the-run; once a newer bond of the same maturity is auctioned, the old one becomes off-the-run. Two 10-year Treasuries issued eight months apart have almost identical cash flows and identical credit risk — they're both backed by the same government — yet the on-the-run bond consistently trades at a slightly higher price (equivalently, a slightly lower yield) than an off-the-run bond with nearly the same maturity.

The gap exists because the on-the-run bond is dramatically more liquid: it's the one dealers quote by default, the one used as a benchmark, the cheapest to borrow and short in the repo market, and the one most actively traded. Investors pay a small premium for that liquidity, the same way people pay slightly more for a house on a street they can resell quickly.

The classic trade, and why it's dangerous

Because the spread is small and historically stable, it invites an obvious trade: short the expensive on-the-run bond, buy the cheap off-the-run bond with matching maturity, and collect the spread as it narrows when the on-the-run bond eventually becomes off-the-run itself (replaced by the next auction) and the two prices converge. This was one of LTCM's signature trades in the 1990s, run at enormous leverage because the spread itself is tiny — a few basis points — and only worthwhile at scale.

Worked example

An on-the-run 10-year note yields 4.50%; an off-the-run 10-year note with nearly the same maturity yields 4.56% — a 6 basis point spread, the off-the-run bond cheaper (higher yield, lower price) because it's less liquid. A fund shorts $500 million of the on-the-run note and buys $500 million of the off-the-run note, roughly duration-matched so the trade is close to neutral to a parallel move in interest rates. If the spread narrows to 3 basis points as expected when the on-the-run note rolls off and a newer note takes its place, the fund captures the difference — a small profit per dollar, which is why the trade is normally run with heavy leverage to be worthwhile.

In August–September 1998, following Russia's debt default, investors around the world rushed into the most liquid, safest instruments available — a flight to liquidity — and that meant an unusually strong preference for on-the-run Treasuries specifically, over economically similar but less liquid off-the-run bonds. Instead of narrowing, spreads like this widened sharply and unexpectedly, moving against LTCM's position at the same moment many of its other convergence trades were also losing money, forcing the fund toward the collapse that led to its Federal Reserve–brokered rescue.

What this means in practice

The on-the-run premium remains a real, persistent, well-documented feature of Treasury markets today, and dealers and relative-value desks still trade around it. But 1998 is the standing reminder that a "safe" liquidity-premium trade can turn dangerous exactly when liquidity itself becomes scarce market-wide, because the very thing you're short (liquidity) is what everyone else suddenly wants at the same time.