Direct Answer
Open interest concentration measures how much of the total open interest in an expiry or chain sits in a few strikes. High concentration means positioning is clustered around particular price levels. A higher share means the chain is dominated by a few strikes, which may then act as reference levels near expiry.
Open Interest Concentration: Formula, Meaning, Signals, Examples and How to Use It
How Is Open Interest Concentration Calculated?
Open interest concentration measures how much of the total open interest in an expiry or chain sits in a few strikes. High concentration means positioning is clustered around particular price levels.
Formula: top-N share = (open interest in the N largest strikes) / (total open interest) x 100; alternatively a Herfindahl index, sum of squared strike shares
Inputs:
- Open interest by strike (calls, puts or both)
- Choice of N or the index form
- Expiries included
Worked example. If the three largest strikes hold 42,000 of 120,000 total contracts, the top-3 share is 35.0%. The inputs are illustrative numbers, not market data.
Reading it. A higher share means the chain is dominated by a few strikes, which may then act as reference levels near expiry. A lower share means open interest is spread across many strikes. Read it against that name's own typical level.
Limits. The result depends on how many strikes and expiries are pooled, and chains with wide strike spacing look more concentrated. It says where contracts sit, not who holds them or why.
What is Open Interest Concentration?
Open interest concentration measures how much of the total open interest in an expiry or chain sits in a few strikes. High concentration means positioning is clustered around particular price levels.
How to use Open Interest Concentration
A higher share means the chain is dominated by a few strikes, which may then act as reference levels near expiry. A lower share means open interest is spread across many strikes. Read it against that name's own typical level. A reading alone is never a buy or sell signal; it needs context from price structure, volume, volatility and the broader market regime.
Strengths
- Taking a top-N share or a Herfindahl index turns a whole strike ladder into one number that is easy to track from day to day.
- The Herfindahl form squares each share, so it rewards one dominant strike more than many moderate ones, which the top-N share does not.
- Reproducible when the formula and data convention are fixed.
Weaknesses and limitations
- Choosing N is arbitrary, and a different N changes how concentrated an identical chain appears.
- Combining calls and puts hides whether the clustering is on one side, so a high reading may reflect offsetting positions at the same strike.
- Correlated indicators can create false confidence by repeating the same underlying information.
Editorial and risk note
This page is educational content, not individualized investment advice. It should not imply guaranteed prediction, accuracy or outperformance.
Frequently Asked Questions
Is Open Interest Concentration a buy or sell signal?
No. A higher share means the chain is dominated by a few strikes, which may then act as reference levels near expiry. The result depends on how many strikes and expiries are pooled, and chains with wide strike spacing look more concentrated. A trade built on it still needs a trigger, an invalidation rule, a position size and realistic execution assumptions.
What is the best setting for Open Interest Concentration?
Open Interest Concentration is computed from open interest by strike (calls, puts or both); choice of N or the index form; expiries included, so the choices that matter are the data convention and the window it is read over. Test those across instruments, regimes and out-of-sample periods instead of fitting one historical winner.
Can Open Interest Concentration be used by itself?
The result depends on how many strikes and expiries are pooled, and chains with wide strike spacing look more concentrated. It says where contracts sit, not who holds them or why. For that reason it is read next to measures of direction, participation, valuation, liquidity and risk, not alone.
Does Open Interest Concentration work on every timeframe?
The calculation (top-N share = (open interest in the N largest strikes) / (total open interest) x 100; alternatively a Herfindahl index, sum of squared strike shares) can be run on any bar size, but behavior is not portable: a reading on a five-minute chart describes a very different market window from the same reading on a daily chart. Validate the exact timeframe before relying on it.
Why does Open Interest Concentration give false signals?
Choosing N is arbitrary, and a different N changes how concentrated an identical chain appears. Combining calls and puts hides whether the clustering is on one side, so a high reading may reflect offsetting positions at the same strike. Lag, noise and regime changes add to this, because market participants react to new information after the reading is calculated.
How should Open Interest Concentration be backtested?
Rebuild Open Interest Concentration from open interest by strike (calls, puts or both) using point-in-time data, write the rules before testing, include delisted securities where relevant, model realistic fills and costs, reserve a validation sample and compare with a simpler baseline.