Quick Answer
For financial futures, the basis reflects cost of carry: the coupon income the cash instrument earns minus the short-term financing cost of holding it to delivery. Carry is positive when the financing rate sits below the instrument's yield, and negative when financing sits above the yield. It is a rate story, not storage or freight.
Physical basis is about storage and moving grain. Financial basis swaps that intuition for interest rates. Here "carry" means what you earn on the instrument minus what it costs to finance holding it.
Cost of Carry for Financial Futures
For a financial futures contract (Treasury notes and bonds, short-term interest-rate futures), the basis between the cash instrument and the futures reflects the cost of carry.
- Cost of carry is the relationship between the yield the cash instrument earns and the short-term financing rate paid to hold it.
- Carry is the coupon income earned minus the financing cost of holding the security to the futures delivery date. Financing is gauged by the short-term repo rate: the interest rate on a short-term borrowing (a repurchase agreement) used to fund holding the security.
- Because carry accrues over the holding period, the futures price is set so it converges to the cash price by delivery, the same convergence seen with physical commodities.
Think of it this way: picture borrowing money short-term to buy a Treasury and hold it until the futures delivers. The coupon is what the Treasury pays you for holding it; the financing rate is what you pay the lender. Carry is simply the first minus the second: your rent collected minus your mortgage.
Positive Carry Versus Negative Carry
The sign of carry depends entirely on which rate is higher: what the instrument yields, or what it costs to finance.
- Positive carry: the short-term financing rate is below the instrument's yield, so the holder earns more in coupon income than they pay to finance the position. Borrowing short-term to hold a higher-yielding, longer-dated Treasury (a normal, upward-sloping curve) produces positive carry.
- Negative carry: the short-term financing rate is above the instrument's yield, so financing costs more than the coupon earns. This is typical when short-term rates sit above long-term yields (an inverted curve).
- The sign of carry tracks the slope between short-term and long-term rates. Short-term financing cheaper than the long-term yield gives positive carry; short-term financing more expensive than the yield gives negative carry. The interest rate analysis unit covers yield curves in depth.
Memory Aid: Carry is coupon minus cost. When what you earn (yield) beats what you pay (financing), carry is positive. Cheap financing under a fat coupon is the positive-carry setup.
Exam Tip: Gotchas
- Positive carry happens when short-term financing is BELOW the instrument's yield; negative carry when financing is above it. Carry is coupon income minus financing cost, so the earning rate has to beat the paying rate for carry to be positive.
- Do not force storage-and-freight intuition onto Treasuries. In financial futures the basis is a cost-of-carry story driven by the short-term-versus-long-term rate spread, not by warehousing or transportation. An inverted curve (short rates above long yields) flips carry negative.