Basis

Basis is best understood as the observable residue of the carry relationship. Under no-arbitrage pricing, a futures price equals the spot price compounded at the risk-free rate over the contract's life, increased by the present value of storage, insurance and financing costs, and reduced by any benefits of holding the physical asset: dividends, coupons, or a convenience yield for commodities in tight supply. Rearranging that identity, spot minus futures equals the benefits of ownership minus the costs of ownership over the remaining term.

This makes the sign of basis informative rather than arbitrary. When storage and financing dominate, futures trade above spot, basis is negative, and the market is in contango. When holders place a premium on immediate physical availability, futures trade below spot, basis is positive, and the market is in backwardation. As time to delivery shrinks, the cost and benefit terms both shrink toward zero, which is why basis mechanically compresses rather than wandering freely.

In financial futures the carry terms are contractual and observable, so basis behaves predictably: for an equity index, it reflects financing cost against expected dividends; for currencies, it reflects the interest rate differential embedded in covered interest parity. Deviations tend to be small and are quickly arbitraged when funding is plentiful.

Commodity markets are where basis becomes an economic variable in its own right. Grain, natural gas and crude oil trade at delivery-point-specific cash prices, and the local basis captures transport bottlenecks, storage capacity and regional demand. A pipeline outage can move the cash price at one hub without moving the exchange-traded contract at all. Treasury futures introduce a further wrinkle: basis is quoted against the futures price multiplied by the conversion factor of a deliverable bond, and the cheapest-to-deliver issue is identified as the one with the smallest net basis, or equivalently the highest implied repo rate.

The practical use of basis is in hedge accounting arithmetic. A producer who holds the cash asset and sells futures achieves an effective realised price equal to the futures price at which the hedge was initiated plus the basis prevailing when the position is unwound. The initial futures price is known, so the only unknown left is the terminal basis. The hedge therefore does not eliminate uncertainty; it exchanges outright price exposure for a much smaller exposure to the spot-futures spread.

Direction matters. A strengthening basis (spot rising relative to futures) benefits the short hedger and hurts the long hedger, and the reverse holds when basis weakens. Basis risk is amplified whenever the hedge is imperfect: a different grade or delivery location, a mismatch between the hedge horizon and the contract expiry, or a proxy asset entirely. Candidates should be able to decompose a hedged outcome into the locked futures price and the basis component, explain contango and backwardation in carry terms, and recognise that rolling a hedge forward through successive contracts introduces a new basis exposure at every roll.