What it means
The starting point is a relationship between two prices. For example, a bond and a futures contract linked to that bond should have a relationship reflecting financing, coupons and delivery rules, and a trader examines whether the actual relationship differs from a defensible valuation.
A common approach buys the relatively cheap instrument and sells the relatively expensive one, so if their prices converge after costs, the combined position earns money. A manager should ask what makes the prices related and what evidence supports convergence.
The trades are often described as market-neutral because offsetting positions reduce broad directional exposure, but that description is approximate. Different maturities, cash-flow shapes and sensitivities can leave interest-rate or yield-curve exposure after the hedge.
Small apparent discrepancies may encourage borrowing to make the return on invested capital larger, but leverage also magnifies losses and margin demands. A tiny unfavourable move can require cash immediately, even if the trader still believes eventual convergence is likely.
Financing is central rather than an incidental expense, because buying a bond while selling a futures contract may require funding the bond through a repurchase agreement, and higher funding rates, larger haircuts or a lender's refusal to renew can undermine the trade. Liquidity can differ across the two legs, since closing one position may be easy while the other has a wide spread or few buyers.
Forced selling during stress can widen the discrepancy that the strategy originally expected to close. Valuation must include coupons, financing, transaction costs and delivery options, because comparing a cash bond's quoted price with a futures price without those adjustments can create a false opportunity, and the instruments may not be as interchangeable as their labels suggest.
The Federal Reserve's analysis of Treasury cash-futures basis trades illustrates both sides, as such trades can help align prices and support demand for securities while their leverage and rapid unwinding can also contribute to market fragility. An investment review should separate expected trading profit from the cash needed to survive adverse moves.
Ask about hedge ratios, collateral, funding maturity, stress losses and exit capacity, because a sound relative-value idea can still fail when its financing ends before its price relationship normalises. Stress tests should include a wider price gap and more expensive funding at the same time.
Those conditions can occur together, making a single-variable sensitivity test too reassuring.
In practice
Real-world examples.
Example
A fund buys a Treasury bond and sells a related futures contract after adjusting for delivery and financing. It expects the price relationship to converge. The analysis includes the bond's coupons and the funding cost until the planned exit.
Example
Two bonds with similar maturities trade at different yields. One has weaker issuer credit and limited trading activity. The apparent gap may compensate for real risk rather than represent a mispricing that an offsetting trade can safely capture.
Example
A leveraged trader expects a $20,000 profit from convergence but faces a $70,000 collateral call after prices diverge. Without cash, it closes at a loss. The eventual market outcome cannot rescue a position that has already been liquidated.
Formula
Calculation
Illustrative economics: expected gross convergence gain $50,000 minus financing $18,000, trading costs $7,000 and other expenses $5,000 leaves $20,000. On $1 million of committed capital that is 2% for the period. A $100,000 adverse valuation move is five times the expected gain and may require extra collateral.
Combined stress: suppose the price gap widens by $60,000 against the trade and financing costs rise by a further $12,000 at the same time. The expected $20,000 profit becomes $20,000 - $60,000 - $12,000 = a loss of $52,000, or 5.2% of the $1 million committed capital. A test that moved only one of the two inputs would show a smaller loss and could give false comfort.Case study
Seen in the real world.
Fictional case: Northbridge Fund proposes a bond-futures trade based on a small price gap. Its risk team discovers that financing must renew weekly while the expected holding period is six months. The fund reduces leverage and reserves cash for a funding shock. It accepts a lower projected return rather than relying on uninterrupted refinancing to keep the trade open.
Northbridge's risk team also sets a written exit rule before the trade begins. If the gap widens beyond a stated loss limit, or if the lender signals that it may not renew funding, the fund closes both legs in an orderly way instead of waiting for convergence. The fictional example shows that the exit plan is as much a part of the strategy as the entry price.
Watch out
Common mistakes.
- Calling the strategy risk-free because its positions offset some market exposure.
- Calculating the price gap without coupons, funding, transaction costs and delivery features.
- Judging expected profit without testing margin calls and the ability to exit both legs.
Questions
People also ask.
Is it just buying bonds?
No. The strategy usually combines related positions to exploit relative pricing. Ordinary bond ownership can seek income or broad price appreciation without that offsetting structure.
Why use leverage?
Price differences can be small, so borrowing can increase the return on committed capital. It also increases funding exposure and the size of potential losses.
Must the prices converge?
No. The relationship can change, the model can be wrong, or convergence can take longer than the financing allows. A trade should be judged under those alternatives.
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