Short the Basis
Short the basis is a trading or hedging position where an investor simultaneously holds a short futures position and a long position in the underlying cash commodity or instrument, profiting if the basis (spot price minus futures price) narrows or goes more negative over time. The strategy is the mirror image of 'long the basis' and is frequently employed by commodity producers, warehouses, and arbitrageurs.
Key takeaways
- The basis is defined as spot price minus futures price; being 'short the basis' means short futures and long cash, so the position profits if basis rises (becomes less negative or more positive).
- In contango markets (futures > spot), a short-the-basis position profits as convergence occurs near expiry — the futures price falls toward spot.
- Commodity producers who have grain or metal in storage and sell futures against it are effectively short the basis; they are exposed to the risk that basis widens (futures rise relative to spot) before they can deliver.
- Basis risk — the risk that spot and futures prices do not move in perfect lockstep — is the primary risk of a short-the-basis position and cannot be fully eliminated.
- Carry costs (storage, insurance, financing) are embedded in the basis and affect the profitability of the position through time.
Explanation
The basis in commodity and fixed-income markets is the arithmetic difference between the cash (spot) price and the relevant futures price. Depending on market convention, basis can be expressed as spot minus futures or futures minus spot; the key is consistency within analysis. In most commodity markets, futures trade at a premium to spot when storage costs and financing are positive (contango), making the basis negative under the spot-minus-futures convention.
A trader who is 'short the basis' holds short futures contracts against a long cash or physical position. The position is profitable when the basis rises — i.e., when spot prices appreciate relative to futures prices, or when futures fall relative to spot. This naturally occurs as futures contracts approach expiry and converge toward the spot price, a process known as basis convergence. In a contango market, this convergence benefits the short-basis trader as the initially negative basis moves toward zero at expiry.
In practice, short-the-basis positions arise in several contexts. A grain elevator operator who purchases corn from farmers and stores it while having sold futures against inventory is running a short-basis book. A gold refiner that has bought physical gold and sold COMEX futures to lock in a price is similarly short the basis. Fixed-income traders who are long cheap-to-deliver Treasury bonds and short Treasury futures are also short the basis in bond terminology.
Basis risk is the critical danger in these positions. The spot and futures markets are linked by arbitrage but not perfectly so: local supply and demand imbalances, transportation costs, quality differentials between deliverable grades, and liquidity mismatches can cause the basis to move contrary to expectations. For example, a sudden regional shortage of a commodity can lift local spot prices well above the futures price, unexpectedly benefiting the short-basis holder — but the converse supply glut can widen the basis adversely. In fixed income, cheapest-to-deliver option value and repo rate fluctuations introduce basis volatility independent of underlying yield movements.
From a risk management perspective, short-the-basis strategies must be monitored for model risk (the basis relationships used to size positions may break down in stressed markets), correlation risk (if spot and futures prices decorrelate), and liquidity risk (inability to exit the futures leg without significant market impact). Historical simulation VaR calculations often underestimate basis risk because periods of high basis volatility are infrequent but highly clustered around supply disruptions or market dislocations.
Formula
Basis = Spot Price - Futures Price; Short Basis P&L = Change in Basis × Position Size
Example
A copper smelter purchases 500 metric tonnes of physical copper at $8,500/tonne (total value $4.25 million) and simultaneously sells 20 COMEX copper futures contracts (each representing 25,000 lbs ≈ 11.34 metric tonnes) at $8,650/tonne. The basis is $8,500 - $8,650 = -$150/tonne (contango). Over three months, the copper futures contract converges toward spot as it approaches expiry. At expiry, spot copper trades at $8,400/tonne and the futures price has converged to $8,400/tonne. Basis is now $0. The smelter loses $100/tonne on the physical ($8,400 - $8,500) but gains $250/tonne on the futures ($8,650 - $8,400), for a net gain of $150/tonne — exactly the initial basis. Total gain: $75,000 (500 × $150), demonstrating that locking in a negative basis and waiting for convergence can be a reliable source of return.
Related terms
Arbitrage Basis Basis Risk Bond Cheapest To Deliver Contango Convergence Correlation Futures Contract Futures Price Gold Hedging