Contango, backwardation and the cost of carry

Open the screen and you will see two prices for the same company. There is the price to buy the share right now, and there is the price of its one-month future — and they are not the same. The future usually sits a little above the stock. Sometimes, oddly, it sits below. New traders reach immediately for the exciting explanation: the future is above because the market expects the stock to rise; it is below because the market expects a fall. The future, they think, is a forecast.

It is almost never a forecast. The gap between the future and the stock is, on ordinary days, a piece of arithmetic — the cost of waiting. Understanding that arithmetic does two useful things. It stops you reading a crystal ball into a number that is really just interest, and it lets you recognise the rare days when the gap stops being arithmetic and starts being a signal of stress.

This module explains where the gap comes from, what its two states are called, and — most importantly — where the tidy formula quietly stops protecting you.

Start with the two prices, named plainly. The spot price is what you pay to own the share this instant, in the cash market. The future's price is what you agree today to settle at a fixed date ahead. The difference between them has a name too: the basis, the gap between the futures price and the spot price.

Why should there be any gap at all? Imagine two ways to end up owning ₹5,00,000 of a stock in one month. Option one: buy the shares today, tying up ₹5,00,000 of your money for the month. Option two: buy the future today, posting only the margin, and keep your ₹5,00,000 earning interest until you settle. Option two lets your cash work for a month. That advantage is worth something — roughly the interest you earn — so the future should cost more than the stock by about that interest, otherwise everyone would prefer the cheaper route and arbitrage would close the gap.

That interest-on-the-money is the heart of the cost of carry: the cost of holding the underlying until expiry. Its main component is the interest you could have earned (or the interest you pay to fund the position). Against it, one thing pulls the other way — dividends. If the stock pays a dividend before expiry, the share owner receives it but the future holder does not, so the future is worth less by the dividend amount. Net it out:

Fair future ≈ Spot + interest to expiry − dividends before expiry.

That is the whole formula, in plain words. The future is the stock's price, plus the cost of carrying it, minus the cash you would have collected by owning it directly. It is a statement about carry, not about direction. It says nothing whatever about whether the stock will go up or down — only what it should cost to defer owning it.

And there is a hard anchor that keeps this honest: at expiry, the future and the spot must converge. On the final day there is no more waiting to pay for, no more dividend to miss, so the carry collapses to zero and the future settles to the spot. Whatever gap you see today is a gap that is contractually going to close. The premium is the price of time, and time runs out on a known date.

The gap has two states, and each has a name worth knowing.

When the future trades above spot — the normal condition, produced by the interest cost of carry — the market is in contango. Most of the time, for most stocks and indices, this is what you see: the near month a little above spot, the far month a little higher still, each extra month adding another slice of carry. Contango is not a warning. It is the resting state of a market where money has a cost.

When the future trades below spot — backwardation — something is pulling the other way. There are two very different reasons this happens, and telling them apart is the whole skill:

• A dividend is due before expiry. This is pure arithmetic. A large dividend is subtracted from the future's fair value, so the future can sit below spot with nothing alarming behind it. The discount is exactly the dividend the future-holder will miss.
• Stress or heavy selling. With no dividend to explain it, a future below spot means a crowd is paying up to be short — to sell the future — or the cash market is being propped while the future sags. That is a genuine signal of fear or forced selling, not arithmetic.

The same discount, then, can mean "routine dividend" or "the market is frightened." You cannot tell which from the number alone; you have to ask what is causing it. This is why backwardation is so often misread — a beginner sees the future below spot and either panics (when it was just a dividend) or shrugs (when it was real stress).

Put numbers on the calm case. illustrative

A stock trades at a spot price of ₹1,000. Short-term interest rates are about 8% a year. The one-month future should carry roughly one month of that interest: 8% ÷ 12 ≈ 0.67%, or about ₹6.70 on ₹1,000. So the fair one-month future is around ₹1,006–1,007. That ₹7 premium is not optimism about the stock. It is one month's interest on the money you did not have to spend buying the shares.

Now suppose the company will pay a ₹20 dividend before this future expires. The future-holder misses that ₹20. Subtract it: ₹1,000 + ₹7 − ₹20 ≈ ₹987. The future now trades below spot — backwardation — and there is nothing frightening in it at all. It is the ₹7 of carry minus the ₹20 of dividend. A trader who did not know the dividend was coming might see ₹987 and imagine the market is bearish. It is not. It is arithmetic wearing a scary costume.

And the anchor holds throughout: whatever the gap today, by expiry the future settles to wherever the spot is. If the stock is ₹1,030 at expiry, the future is ₹1,030 — the ₹7, or the −₹13, has bled away to zero as the days ran out. The basis is not free money and not a forecast; it is the melting price of time.

Everything above describes the market on an ordinary day, and on ordinary days it is genuinely reliable — arbitrage keeps the future glued to spot-plus-carry, because if it drifted too far, professionals would buy the cheap leg and sell the dear one until the gap closed. This is the comforting part, and it is real.

Here is where the comfort becomes dangerous. The neatness of the carry formula tempts people into believing futures pricing is safe — that because the relationship is tidy and arbitrage-enforced, a position built around it carries little risk. This is a category error. The cost-of-carry formula tells you the fair gap on a normal day. It tells you nothing about the size of the move on an abnormal one.

On the violent day, three things happen at once, and the formula covers none of them. Prices gap — the stock and its future can leap 10–15% overnight on news, before you can act. The basis itself lurches — in a panic the tidy ₹7 can blow out or invert as arbitrage temporarily breaks and everyone reaches for the exit at once. And margins spike — as we saw in the previous module, SPAN margins jump exactly then, calling for cash at the worst moment. A "low-risk carry" position can be wrecked by a single session the smooth formula never contemplated.

This is the fat-tail caveat, and it is the spine of this whole Reading in a new disguise. The rare, large jump is not an exception to the rule — it is where the real money is made and lost, and the calm formula is silent about it precisely there. A model that is right 98% of the time can still ruin you, because leverage means the 2% is where the account lives or dies.

The carry gap is quietly one of the most misread numbers on the screen.

1. Reading the premium as a forecast. A future above spot is not the market predicting a rise. It is interest — the price of waiting. It converges to spot by expiry regardless of where the stock goes.

2. Panicking at every backwardation. A future below spot is often just a dividend being subtracted. Check whether a dividend is due before deciding the market is frightened.

3. Thinking the gap is free money. "The future is ₹7 higher, so I'll short it and pocket the ₹7" ignores the interest you forgo and the risk you carry. The gap is compensation for a real cost, not a gift lying on the floor.

4. Trusting the formula through a storm. Cost of carry is a calm-day relationship. In a panic the basis dislocates, prices gap, and margins spike — and the formula says nothing about any of it.

5. Forgetting convergence. Whatever premium or discount you see today, it melts to zero by expiry. A carry trade's return is that melt — small, and easily swamped by one adverse gap.