Futures Roll-Over: Interpreting Basis, Cost-of-Carry & Open Interest

Basis

The basis is simply:

Basis = Futures Price − Spot Price

If futures are trading higher than spot, you have a positive basis; if lower, a negative basis (less common in equity index futures). The basis captures expected costs and benefits of holding the underlying until expiry (dividends foregone, interest cost, etc.). For Indian index futures, this number varies across expiries and reflects the cost of carry plus market expectations.

Cost‐of‐Carry

Cost-of-carry measures the cost to hold the underlying asset (or maintain equivalent exposure) until the futures expiry. It includes interest cost (funding your position) less any yield/dividends you receive on the underlying, plus other costs (storage, maintenance) for physical assets. In formula form:

F = S × e^{(r + s − c) × t}

where F = futures price, S = spot, r = risk-free interest rate, s = storage/other costs, c = convenience yield/dividend yield, and t = time to expiry.

In equity index futures: cost of carry roughly equals (funding cost + expected dividends) over the remaining months to expiry. A high cost-of-carry means futures trade significantly above spot (wide basis). Lower cost means futures are closer to spot.

Why this matters: If you buy long futures, a large positive cost-of-carry adds to your breakeven; if you are short, you may benefit if the roll is favourable.

When rolling over you are essentially paying or receiving the spread between the near-month futures and the next-month futures. That spread is a practical cost (or benefit) of staying exposed. For example, if June futures trade at 17,000 and July futures at 17,050 when spot is 16,900, you pay a roll cost of 50 points.

Key interpretations:

• Large positive basis / high roll cost: suggests higher funding cost or high dividend expectations; staying long becomes more expensive.
• Declining basis: could mean dividends expected are low, or interest rates are falling — might favour long exposure.
• Negative basis (rare in equity indices): would suggest market expects downward drift or large negative yields.

Tracking the roll cost across months gives you a sense of how much extra return you need to earn on the futures to justify holding. For example, if you pay 0.30% of the contract value to roll, your view must earn more than that to breakeven.

Open Interest (OI)

Open interest (OI) is the number of outstanding futures contracts (long + short) that have not been closed or settled. It reflects how many participants are holding positions. Changes in OI along with price movement help interpret whether new money is entering the market or existing positions are being unwound.

Rollover Percentage

This metric shows how much of the current-month contract’s open interest is carried into the next contract. For example, if 100 lakh contracts exist in the June series and 80 lakh of those are open in the July series, the rollover percentage is 80%.

High rollover percentage suggests strong conviction among traders—the majority are choosing to maintain exposure rather than close. Conversely, a low rollover percentage may signal lack of conviction or profit-taking.

Interpreting OI and Rollover Data

• Price up + OI up → new long positions entering; bullish signal.
• Price up + OI down → short covering dominates; weaker bullish signal.
• High rollover % + strong spread → indicates traders willing to pay cost to remain; bullish tilt.
• Sharp drop in rollover % → could warn of rollover risk and potential liquidity squeeze in new contract.

Here’s How You Can Use These Metrics

1. Monitor basis & roll cost a few days before expiry
Platforms (like 5paisa) provide data on current/next contract futures prices. Calculate the spread and compare with historical averages to judge cost.

2. Check rollover percentages
High rollover %, especially in index futures (Nifty, Bank Nifty), often signal continuation of trend. For example, a report showed Nifty rollover of ~79% in one month.

3. Align trade horizon with cost implications
If cost of carry is high and you are long futures anticipating a small move, the net return may flip negative after cost.

4. Use OI movements to validate price action
If price rises but OI falls sharply, the move may be fuelled by short covering — less sustainable.

5. Use roll-over information as sentiment gauge
Rollover data in India is often interpreted as a bulls-vs-bears strength measure; for example, when rollover cost stays high and rollover % remains strong, bullish bias persists.

Things to Watch Out For

• Liquidity & slippage in next contracts: Moving to further-out month may involve wider spreads and lower liquidity, increasing cost beyond the visible spread.

• Unexpected corporate/dividend events: For stock futures, the cost of carry may shift sharply if a large dividend is announced, affecting the basis.

• Regulatory/contract changes: In India, exchanges may change contract specs, notional, or expiry schedule — these changes affect roll cost unpredictably.

• Cost of carry estimates are approximate: The actual cost of carry depends on actual dividends, interest rates, and market demand — so basis alone is an indication, not an exact measure.

• Misreading OI flows: Open interest increases can mean new longs or new shorts — context with price movement is essential; a simple rise in OI is not always bullish.