Open interest and options flow: how to read OI for institutional positioning

Volume vs open interest: the core distinction

Every options analysis post will mention volume and OI, but the distinction matters enough to state clearly:

Volume is the number of contracts traded today. It resets to zero at the start of each session. If 15,000 NVDA $140 calls traded on Tuesday, Tuesday's volume for that contract is 15,000. Wednesday's volume starts at zero.

Open interest is the number of contracts currently outstanding, they have been opened but not yet closed, exercised, or expired. OI is updated once per day (typically after market hours by the OCC). It does not reset daily; it accumulates over time as contracts are created and declines when contracts are closed, exercised, or expire.

Two contracts are created for every option transaction: one for the buyer (long) and one for the seller (short). OI increases by one for each new pair. When an existing buyer sells to a new buyer, OI stays the same, ownership changes but the total outstanding contracts do not. When an existing buyer sells back to an existing seller (both sides closing), OI decreases by one.

For flow analysis, this distinction matters because it determines what today's volume actually represents.

The Vol/OI ratio: new positioning vs noise

The Vol/OI ratio, today's volume divided by yesterday's open interest, is the single most important ratio in options flow analysis. Here is why:

If a strike has 10,000 contracts of existing OI and today's volume is 2,000, most of that volume could be existing holders closing or rotating their positions. OI was 10,000; 2,000 new contracts would barely change the picture. Low signal.

If the same strike has 10,000 OI and today's volume is 25,000, there are simply not enough existing contracts to explain that activity as position closing. The volume must represent new positioning, someone opened 15,000+ new contracts today. High signal.

The Vol/OI ratio works best in names that do not have enormous baseline OI from sustained institutional interest. For very high-OI names (SPY, QQQ, AAPL, NVDA at peak attention), the denominator is so large that even massive dollar-value sweeps can produce compressed ratios. For those names, see the section on high-OI limitations below.

OI as a map of existing institutional positions

Open interest is not just a denominator for Vol/OI calculations. The distribution of OI across strikes and expirations is itself a map of where institutional positions currently exist.

A strike with very high OI relative to neighboring strikes represents a location where a significant number of contracts, and the institutions who own or are short them, have a vested interest in price behavior around that level. This is the foundation for two OI-based phenomena: the OI gravity effect and the OI support/resistance effect.

OI gravity near expiration

As an options expiration approaches (typically the last two weeks before monthly expiration), the stock price tends to be "pulled" toward strikes with the highest total OI. This is not magic; it is a mechanical result of market maker hedging.

Market makers who are short options to buyers must delta-hedge by buying the underlying (for long calls they are short) or selling it (for long puts they are short). As the stock price moves toward a high-OI call strike, market makers must buy more stock to hedge, which creates buying pressure. As the stock dips away from that strike, market makers sell back, creating selling pressure. The net effect is price gravity toward the high-OI strike in the final days before expiration.

This is the basis for the "max pain" concept: the price that minimizes the total value of outstanding options (i.e., the price at which most options expire worthless). Max pain is simply the weighted average center of OI, and it describes the price to which gravity pulls the stock in the expiration week. For active traders, this is useful context, a stock sitting at $148 two days before expiration with 50,000 calls OI at $150 and 40,000 puts OI at $145 is likely to see choppy price action as it gets pushed and pulled between those two gravity wells.

OI support and resistance

High call OI strikes tend to act as resistance. When a stock approaches a strike with very high outstanding call OI, market makers who are short those calls must sell the underlying stock as they delta-hedge, creating selling pressure at that level.

High put OI strikes tend to act as support. Market makers short those puts must buy the underlying as the price approaches that level, creating buying pressure.

This is a probabilistic tendency, not a mechanical rule. It is strongest in the week or two before a major expiration and weakest immediately after expiration (when OI clears and the positioning landscape resets).

Overnight OI change: reading what positions were held

One of the most underused OI signals is the overnight change in OI between sessions. The calculation:

OI change = (Today's OI at a strike) − (Yesterday's OI at that strike)

If yesterday's OI at the $170 MSFT call was 5,000 and today it is 12,000, OI increased by 7,000 overnight. Yesterday's volume was, say, 9,000. That means at least 7,000 of yesterday's 9,000 contracts were new positions that were held overnight, not closed at end of day.

Overnight OI increase is significant because it tells you the positions were kept. A large sweep that closes before the end of session adds to volume but not to OI. A large sweep that is held overnight appears in both volume AND overnight OI. The holder decided their position was worth keeping, a higher-conviction signal than a print that closed the same day.

When overnight OI increases significantly at a specific strike and the premium involved is large, it implies an institution opened a new position and held it, suggesting a multi-day or multi-week thesis, not a same-day trade. That is the institutional behavior patterns that flow analysis is looking for.

OI changes across multiple sessions

Tracking OI changes across three to five sessions at the same strike produces an accumulation picture without needing the real-time tape. If the $200 call strike in a name sees OI increase by 5,000 on Monday, 3,000 on Tuesday, and 4,000 on Wednesday, totaling 12,000 new contracts held overnight, an institution (or institutions) is building a position. This is the OI equivalent of the multi-session tape momentum signal.

OI and option rolling patterns

Rolling is when an institution closes a position in a near-term expiration and reopens a similar position in a further-out expiration. It appears in the OI data as a simultaneous decline in near-month OI and increase in the next month (or quarter).

Bullish roll

OI in the March $150 call falls by 10,000 contracts (they are being closed). OI in the June $155 call rises by 8,000 contracts (new position being opened). This is a bullish roll: the institution's directional thesis is intact (still bullish), but they need more time, either the catalyst is taking longer than expected or they have information suggesting the move will occur in Q2 rather than Q1.

Bullish rolls are constructive for the thesis, the institution has not abandoned the view; they have extended the time window. Treat a bullish roll as a confirming signal for existing watchlist positions.

Bearish roll

The same pattern in puts. Near-term put OI falls, further-out put OI rises. The institution remains bearish but extended their horizon.

Position close (not a roll)

Near-term call OI falls significantly with NO corresponding increase in next-month OI. The institution has exited their position outright. If this happens in a name where you hold a position based on the original call flow, treat it as a signal that the original informed participant has left, which significantly reduces the thesis strength. Consider reducing or exiting.

High-OI names: where Vol/OI becomes unreliable

The Vol/OI ratio has a known limitation in very high-OI names. SPY, QQQ, IWM, AAPL, NVDA during periods of high attention, and other mega-cap names with sustained institutional interest have enormous baseline OI across hundreds of strikes. Even a $5M sweep in one of these names may produce a Vol/OI ratio of 0.4×, not because the trade is unimportant, but because the denominator (existing OI) is so large.

For high-OI names, two alternative approaches:

Absolute volume vs trailing average: Instead of Vol/OI, compare today's volume at a specific strike to the trailing 5-day average volume at that same strike. If the average is 500 contracts and today's volume is 6,000, that is a 12× spike, potentially significant regardless of what OI is doing.

OI change approach: Focus on overnight OI changes rather than Vol/OI ratios. A large overnight OI increase in a high-OI name still represents new positioning that was held, even if the Vol/OI ratio is compressed.

Using OI in the flow scoring framework

OI appears explicitly in the flow scoring model as the Vol/OI component, which carries 30% weight in the overall conviction score. The scoring breakpoints:

• Vol/OI 2× to 3× → moderate score contribution (~50% of maximum)
• Vol/OI 3× to 7× → good score contribution (~75%)
• Vol/OI 7× to 15× → high score contribution (~90%)
• Vol/OI above 15× → maximum contribution (effectively capped; beyond this level the signal quality is already high and the incremental information is limited)

OI also implicitly affects the premium size score (40% weight). A $500K sweep in a name with 50,000 OI represents a small fraction of existing positions and therefore carries less conviction than the same $500K in a name with 200 OI, where the sweep represents a massive new claim on the name.

OI as a watchlist management tool

Open interest is useful not just for evaluating individual prints but for managing the watchlist over time.

Watching for position exits: If a name is on your watchlist based on bullish call flow, and you notice OI in the relevant strike declining significantly over the next week without a corresponding price move, the institution may have changed their mind or taken a loss. Declining OI in the watchlisted strike reduces conviction; consider removing the name.

Watching for rolling: OI declining in the near-term expiration paired with OI increasing in the next-month at the same or higher strike is a bullish roll, the institution extended, not abandoned. Keep the name on the watchlist.

Watching for OI buildup in the opposite direction: If call-based bullish watchlist name starts accumulating significant put OI at lower strikes (a separate party buying puts at the same time calls are being accumulated), the picture is more mixed. This could be straddle construction, a different institution hedging the same name bearishly, or the original institution partially hedging their long calls. Reduce conviction accordingly.

Practical OI reading checklist

When evaluating any large options print for institutional signal:

1. Check Vol/OI at the specific strike. Is it above 2×? Above 5×? This determines whether the print is new positioning or existing rotation.
2. If Vol/OI is below 2× in a high-OI name, check today's volume vs the 5-day average at that strike. Is there a volume spike even if the ratio looks compressed?
3. Look at overnight OI change tomorrow morning. Did yesterday's volume result in meaningful OI growth? If yes, the position was held, institutional intent.
4. Check OI distribution across strikes for the relevant expiration. Where are the concentration points? Is the strike in your flow print near a high-OI gravity point that would support or resist price movement?
5. Track OI changes over the next three to five sessions for any watchlist name. Steady OI increase confirms accumulation. OI decline with no price move may indicate the institution is exiting.
6. Watch for rolling patterns as the expiration approaches. Near-term OI falling + next-month OI rising = institution extending, not exiting.

Gamma exposure and OI: when dealer positioning drives price

The gamma squeeze is one of the most discussed phenomena in modern options markets, and one of the most misunderstood. The mechanics behind it are rooted directly in open interest. To understand why gamma squeezes occur, and how to read OI data in anticipation of them, you need to understand how market maker gamma exposure interacts with outstanding option positions.

When an institution buys call options, creating long call OI at a given strike, the market maker on the other side of that trade is short those calls. To hedge their short call position and maintain a delta-neutral book, the market maker buys the underlying stock in proportion to the option's delta. As the stock rises and the calls move deeper in-the-money, delta increases, meaning the market maker must buy more stock to stay hedged. That additional buying pushes the stock price higher, which forces more buying. This is the gamma feedback loop: rising price forces more buying, which forces the price higher, which forces more buying.

The magnitude of this self-reinforcing effect depends directly on open interest. A name with 100,000 call contracts outstanding at a strike $5 above the current price will experience dramatically more mechanical buying from dealer delta-hedging as the price rises through that strike than a name with 10,000 call contracts at the same level. OI is the multiplier on the gamma feedback effect, more OI means more contracts requiring hedge adjustments, means more mechanical trading activity generated by price moves in either direction.

Net gamma exposure (GEX) quantifies this at the portfolio level. The formula: total net gamma exposure equals the sum of (strike gamma × OI at each strike × contract multiplier, typically 100) across all strikes, with calls positive and puts negative. When net GEX is positive, meaning more call OI is outstanding above the current price than put OI is outstanding below, dealer hedging tends to amplify upside moves. As prices rise, dealers buy more; as prices fall slightly, dealers sell. This creates a "pinning" effect where large positive GEX environments tend to have lower realized volatility. When net GEX is negative, more put OI concentrated below current price, dealer hedging amplifies downside moves, which is why market sell-offs often feel as though they have an accelerating component.

The negative gamma environment is particularly important during market stress. When substantial put OI exists below the current market level, as institutions buy index puts for portfolio protection, dealers are short those puts. As the market declines toward those puts, dealers must sell more of the underlying to stay delta-neutral. This selling accelerates the decline, which requires more selling, in a feedback loop that mirrors the bullish gamma squeeze but in reverse. This mechanical dynamic explains much of the "air pocket" behavior seen during sharp market corrections: negative net GEX is converting dealer hedging activity into a selling engine at precisely the moment when fundamental sellers are also active.

What this means for flow analysis is concrete. When you observe a large new call sweep landing in a name that already carries substantial call OI at strikes above the current price, the gamma dynamics work in the call holder's favor. Market maker hedging provides a mechanical tailwind as the stock approaches those strikes, augmenting whatever fundamental catalyst the positioning implies. Conversely, large put sweeps that are building OI at strikes below current price establish the preconditions for mechanical selling pressure on any downside move.

The expiration reset is the final piece. All gamma exposure resolves at expiration. When options expire, their OI clears and the associated gamma exposure vanishes. This is why names frequently experience sharp moves immediately after major expirations, the mechanical forces that were pinning the price toward high-OI strikes are removed simultaneously. The stock moves to its "true" equilibrium free from the influence of dealer hedging. Monitoring OI distribution going into major expirations, and tracking the change in OI distribution immediately after expiration, gives you a read on when gamma-driven mechanical forces are entering or leaving a name.

OI term structure: reading the expiration landscape across months

Open interest does not exist at a single expiration, it is distributed across the complete chain of available expirations, from the nearest weekly to LEAPS contracts two or more years out. The pattern of how OI is allocated across this term structure is one of the most revealing and underread signals in options flow analysis. It answers a question that raw volume data cannot: what time horizon is the institution targeting?

Monthly vs weekly OI concentration. Standard monthly expirations, the third Friday of each month, accumulate the highest OI in most names because they have the longest trading history, the broadest market participation, and the highest liquidity for rolling. Weekly expirations typically carry lower total OI but concentrate positioning activity around specific near-term catalyst events: Federal Reserve meetings, CPI and PPI release dates, earnings announcements, FDA PDUFA decisions, and major product launch windows. A name that is showing OI accumulation in a specific weekly expiration rather than the surrounding monthly is almost always being positioned around a specific dated event.

The pre-earnings OI cliff. In the three to four weeks before a company's earnings announcement, OI in the post-earnings expiration builds at an accelerating rate. This is one of the most predictable OI dynamics in the options market: institutional participants accumulate positions in the first expiration after the earnings date to capture the directional move and the implied volatility elevation before the report. By the day before earnings, OI in the post-earnings monthly can be three to five times the OI that same series carried during non-earnings periods. Observing this ramp in real time provides a leading signal, a name that is historically modestly traded options-wise but is showing aggressive OI growth in the post-earnings expiration three weeks out is drawing more institutional attention to the coming report than usual. The ratio of call OI to put OI accumulating in that expiration serves as one indicator of market-implied directional sentiment going into the announcement.

Reading "skipped" expirations. When an institution wants to position for a longer-duration thesis rather than a near-term catalyst, they frequently skip the next one or two expirations and concentrate OI in a further-out monthly. A name where the nearest one to two expirations carry modest OI but the 90-day or 120-day expiration has very high call OI is almost certainly receiving a multi-month directional bet rather than a near-term catalyst play. The choice of expiration reveals the institution's time horizon, which in turn informs how you should interpret the underlying thesis. A 90-day call position is a different conviction level and a different type of catalyst expectation than a two-week position.

LEAPS OI as a long-duration conviction signal. Long-Term Equity Anticipation Securities, options with 12 to 24 months to expiration, with very high OI represent institutional conviction about the multi-year directional trajectory of a stock. LEAPS OI builds slowly and rarely moves quickly. When LEAPS call OI begins increasing significantly at above-market strikes over a period of weeks, it signals that institutions are purchasing long-duration upside. This pattern is associated with early-stage positioning in major fundamental theses: pre-M&A target accumulation, early positioning in emerging technology themes before the thesis becomes consensus, and commodity supercycle bets in energy, materials, and agriculture sectors. LEAPS OI changes are slow-moving but highly informative about multi-year conviction.

How to use the term structure in practice. Map the OI distribution across all available expirations for any name that appears in your flow watchlist. The key questions to answer are: Where is OI most heavily concentrated? Is there a visible step-change in OI around a particular calendar date that might explain the institutional timing preference? Is OI building faster in near-term expirations (suggesting a near-term catalyst) or in far-term expirations (suggesting a multi-month thesis)? A name where OI is steadily growing in the 90-day expiration while near-term expirations remain flat is being accumulated for duration, a patient, conviction-driven position rather than a quick catalyst play.

Put/call OI ratio as a market-structure signal

The put/call ratio based on open interest, total put OI divided by total call OI, commonly written as PCR, is one of the oldest sentiment indicators in options analysis and one of the most consistently misread. Understanding what the PCR actually measures, and when its simple interpretation fails, is essential for using it correctly alongside flow data.

What the ratio measures on the surface. A PCR above 1.0 means more put OI is outstanding than call OI, more bearish positioning or more hedging demand. A PCR below 1.0 means more call OI, more bullish speculative positioning. The naive interpretation: low PCR is bullish; high PCR is bearish. That interpretation is directionally correct at the extremes but gets the mechanism wrong in the middle, which is where the real analytical value lives.

Why the simple interpretation fails. The put/call OI ratio simultaneously reflects two completely different types of activity: speculative directional bets and institutional portfolio hedging. During risk-off periods, market corrections, geopolitical shocks, macro uncertainty events, institutional fund managers buy put options aggressively to protect their long equity portfolios. This hedging activity drives the PCR substantially higher. But this does not mean the market is imminently about to collapse; it means the institutions who hold equity are paying for downside insurance. A high PCR in a market that is still grinding higher, or that is recovering from a sell-off, often reflects exactly this hedging-driven dynamic. The equity holders are hedged, not net short.

The contrarian signal at extremes. The PCR delivers its most reliable information at extremes rather than in the middle range. An extremely low PCR, meaning call OI is overwhelming put OI, minimal hedging demand, indicates widespread market complacency. When nearly everyone is positioned for upside and almost no one is paying for protection, the market is exposed to a sentiment shock. A correction in this environment can be sharper than fundamentals justify because unhedged longs all rush to sell simultaneously. Conversely, an extremely high PCR, maximum put protection in place across the institutional universe, often marks a near-term market bottom. When so much downside protection is already outstanding, the incremental selling pressure from new hedging is limited. The market has already priced in the fear; the shock has been absorbed into OI. This is why extreme PCR levels are sometimes used as contrarian indicators, not for precise timing, but for identifying when sentiment is at an actionable extreme.

PCR for individual stocks carries more directional information. The index-level PCR (on SPY, QQQ, SPX) is dominated by hedging demand and carries less speculative directional signal. Individual stock PCR, particularly for mid-cap names that are not commonly used as macro hedge vehicles, carries more pure directional information. A high PCR building on a specific mid-cap consumer stock is more likely to reflect actual bearish positioning than the same ratio on the S&P 500. For individual names, a rising PCR alongside declining price may indicate institutional capitulation or building bearish conviction. A falling PCR alongside rising price may indicate genuine sentiment improvement as protection is unwound.

Using PCR alongside intraday flow. A name where you are seeing aggressive call sweeps but the overall PCR is simultaneously rising, more put OI building in the background while calls are being added, presents a genuinely mixed signal that warrants further investigation. Two common explanations: first, the call sweeper and the put builder are different institutions with opposite views, representing a genuine divergence in institutional opinion. Second, the call sweeper may be the same institution running a collar strategy, buying calls to express upside while simultaneously adding puts to define downside risk. In either case, the divergence between aggressive call flow and rising PCR reduces the conviction level of the bull thesis relative to a clean call-only accumulation signal.

OI changes around earnings and high-impact events: what the data reveals

Earnings announcements and other scheduled high-impact events, Federal Reserve meetings, major economic data releases, FDA drug decisions, product launches, create the most significant and predictable OI dynamics in the options market. The pattern of how OI builds before these events and clears afterward is one of the most actionable signals in event-driven flow analysis.

The pre-earnings OI buildout timeline. In the 15 trading days before an earnings announcement, OI in the post-earnings expiration builds at a rate that accelerates as the date approaches. The buildup begins modestly, perhaps 20 to 30 percent above baseline, roughly three weeks out, then steepens sharply in the final week, peaking in the last two or three trading sessions before the announcement. The total accumulated OI increase during this period can be two to four times the baseline OI that the same strike and expiration carried during the prior non-earnings cycle. Tracking this ramp in real time is itself a signal: a name that historically sees quiet pre-earnings positioning but is showing early aggressive OI buildup three weeks before the report is drawing institutional attention that suggests unusual conviction or information about the coming quarter's results.

OI skew as an earnings sentiment read. As pre-earnings OI accumulates in the post-earnings expiration, the distribution between call OI and put OI at that expiration reveals the implied directional sentiment of the market going into the report. A name where call OI in the post-earnings expiration is running 1.8 times put OI has more bullish speculative positioning than bearish hedging, the market is implicitly pricing a beat-and-raise as the base case. If put OI is matching or exceeding call OI, the market is either more uncertain or more bearish about the coming print. This read is imperfect, some of the put OI is portfolio protection from long holders rather than directional shorts, but the directional skew in a specific name's post-earnings OI is informative context for interpreting the associated flow data.

Post-earnings OI flush and what it reveals. Immediately after an earnings announcement, implied volatility collapses dramatically, the event risk has resolved, and the majority of OI that was accumulated for the catalyst closes out. Holders who made money take profits; holders who lost money cut losses; hedgers who bought protection no longer need it. This post-earnings OI clearing is often dramatic: OI at post-earnings strikes frequently falls 60 to 80 percent within two trading sessions of the announcement. Monitoring this OI flush reveals how the smart money was positioned and whether they are exiting completely or partially retaining exposure. If a bullish call position sees only 40 percent of its OI close after an earnings beat, the remaining 60 percent stays open, the institution may be extending the thesis rather than exiting. If all the OI closes immediately on the announcement day, the trade was purely tactical. The residual OI after the event is the signal worth watching.

Fed meeting OI dynamics. FOMC meetings, eight per year, create an OI dynamic in index ETF options rather than individual names, because the Fed's rate decisions affect all equities simultaneously. In the five trading days before an FOMC announcement, monitor SPY and QQQ OI for shifts in the put/call distribution. Pre-FOMC put OI accumulation in index options indicates institutional hedging ahead of a potentially hawkish surprise; pre-FOMC call OI accumulation implies positioning for a dovish surprise or a "hold with dovish language" outcome. The magnitude of OI growth relative to the trailing non-FOMC baseline indicates how much uncertainty the market is pricing into the decision. Very low pre-FOMC OI growth implies the outcome is considered highly predictable; very high growth indicates genuine two-sided uncertainty.

PDUFA dates and biotech OI: binary event extremes. FDA drug approval decisions, known as PDUFA dates, the Prescription Drug User Fee Act deadline by which the FDA must make a decision, represent the most binary high-impact events in the options market. A positive approval decision may push a clinical-stage biotech 50 to 100 percent higher; a complete response letter (rejection) may push it 50 to 80 percent lower. Pre-PDUFA OI in biotech names is extreme by any normal standard. Implied volatility frequently reaches 150 to 400 percent as the date approaches, and OI concentrations build at both call and put strikes simultaneously as different participants place directional bets or straddle the event. The distribution of pre-PDUFA call OI versus put OI, whether the call side is carrying more aggregate premium than the put side, is one of the few available reads on how the options market is implicitly weighting the approval probability. Monitoring PDUFA calendar dates and watching for OI buildout beginning 15 to 20 trading days before the decision is one of the highest signal-density applications of event-driven OI analysis.

Case studies: OI patterns before three major moves

The following three cases illustrate how the OI signals described throughout this guide appear in practice, what the data shows before and after the move, and what the key analytical lesson is from each pattern. These are constructed from the types of patterns that appear repeatedly in institutional flow data, the numbers and contexts are representative of real observable dynamics.

Frequently asked questions

What is the difference between open interest and volume in options?

Volume is contracts traded today, it resets to zero each session. Open interest is the total outstanding contracts currently open, it accumulates over time. Volume tells you what is happening today; OI tells you what institutional positions exist. For flow analysis, the ratio of volume to OI (Vol/OI) determines whether today's activity is new positioning or existing position rotation.

What is the Vol/OI ratio and why does it matter for flow analysis?

Vol/OI divides today's volume by existing OI. Above 2× means the activity exceeds the existing position stock, it must be new positioning rather than people closing what already exists. Above 5× is high conviction new positioning; above 10× is extreme. The ratio is the core filter because it separates new institutional bets from routine rotation.

What are OI concentrations and how do they affect price?

Strikes with high OI become price magnets near expiration because market makers delta-hedge their short options by trading the underlying. High call OI above current price creates resistance; high put OI below creates support. The highest combined OI strike is often called max pain and tends to attract price in the final week before expiration.

What does an overnight OI change tell you?

An OI increase overnight means yesterday's volume included contracts that were held rather than closed. An institution bought those contracts and decided to keep them, a higher-conviction signal than a print that was closed the same day. Large overnight OI increases in the direction of existing flow confirm accumulation intent.

What is option rolling and what does it reveal about institutional intent?

Rolling is closing a near-term position and reopening in a further-out expiration. Near-term OI declining while next-month OI rises at the same or higher strike means the institution extended their time window, the thesis is intact but the catalyst is taking longer. Treat bullish rolls as thesis confirmation for existing watchlist positions.

Why does high OI in a name make flow analysis harder?

Very high baseline OI compresses the Vol/OI ratio, even a $5M sweep may produce a 0.4× ratio because the denominator is enormous. For high-OI names, use absolute volume vs the 5-day average at that specific strike, or focus on overnight OI changes rather than the ratio itself.