Summary. Option order flow contains information about future stock prices, but raw "unusual activity" feeds mix that information with hedges, spreads, rolls and liquidity provision. This article reviews the evidence that option volume is informative, explains how trades are classified as buyer or seller initiated, shows how open interest changes separate opening from closing activity, and proposes a five-stage filter that combines these signals with the dealer positioning map.
1. Is option flow informative?
The academic answer is yes, under conditions. Easley, O'Hara and Srinivas show that informed traders use options when leverage and liquidity make them attractive, and that signed option volume leads stock price changes [1]. Pan and Poteshman build put-call ratios from option volume initiated by buyers to open new positions; stocks with low ratios outperform stocks with high ratios by more than 40 basis points the next day and by more than 1% over the next week on a risk-adjusted basis. The effect is stronger for stocks with a higher concentration of informed traders and for options with more leverage [2]. The common thread is that the informative part of flow is directional, opening, and initiated by end users. Most of the remaining volume is not.
2. Sweeps and blocks
- Sweeps are orders split across exchanges to take available liquidity immediately, usually sent as intermarket sweep orders. The buyer pays the spread at several venues to get filled now. Urgency is the signal, and repeated same-direction sweeps in one contract are the strongest form of it.
- Blocks are large trades negotiated as a single print, often by institutions. They carry size but ambiguous intent: a block can be a hedge against a stock position, one leg of a structure, or a roll of an existing position.
Sweeps indicate aggression; blocks indicate size. Neither, on its own, tells you whether the position is new or directional.
3. Who initiated the trade
The same print is bullish or bearish depending on which side crossed the spread. The standard approach is the quote rule refined by Lee and Ready: trades at or above the ask are buyer initiated, trades at or below the bid are seller initiated, trades inside the spread are classified by their position relative to the midpoint, and trades exactly at the midpoint fall back to a tick test [4]. Figure 1 summarizes the rule.
Classification matters for prices as well as for direction. Muravyev shows that order imbalances in options move option prices, consistent with market makers charging for inventory risk, so aggressive buying is costly and therefore informative about the buyer's conviction [5].
4. Opening or closing: volume and open interest
Each option trade changes open interest by +1, 0 or −1 contract depending on whether both sides open, one opens and one closes, or both close. Over a day,
Two consequences are useful:
- If daily volume exceeds the prior day's open interest (), the day's trading cannot consist only of closing trades, so at least part of it is new positioning.
- The next open interest report confirms the net result [6]. A large buyer-initiated print followed by an open interest increase of similar size is strong evidence of a new position. No increase suggests a close or a same-day round trip.
5. Common sources of noise
- Spread legs. A large call print that is one leg of a vertical spread, a risk reversal or a calendar is hedged by its other legs. Reading one leg alone is the most frequent error in flow analysis. Multi-leg trades are often reported with a condition code that identifies them.
- Stock-tied trades. Deep in-the-money options traded with stock (for example in dividend or conversion strategies) are mechanical.
- Rolls. Closing one expiry and opening the next produces large volume without a change in the overall view.
- Market maker inventory trades. Two-sided liquidity provision raises volume without adding directional positioning.
- Expiration flow. Volume clusters around expirations for mechanical reasons.
6. Flow in the context of dealer positioning
The price impact of a directional position depends on how dealers hedge the other side. Customer call buying leaves dealers short those calls. If the strike is near spot and the market is already in a short-gamma regime, the dealers' hedge buying as spot rises can reinforce the move. If dealers are long gamma overall, the same flow is more likely to be absorbed. This is the same feedback channel studied by Ni, Pearson, Poteshman and White [7]. The gamma flip and the walls provide that context.
7. A five-stage filter
- Screen for size and premium relative to the contract's normal activity.
- Remove linked trades: spread legs, rolls and stock-tied trades.
- Estimate opening versus closing with volume relative to prior open interest, then confirm with the next open interest report.
- Classify the aggressor with the quote rule and tick test.
- Place the result on the dealer map: regime, distance to walls, and whether the new position adds to or offsets dealer gamma near spot.
The output of the filter is a short list. That is the intended result: most large prints are not directional bets, and the few that are become easier to see once the rest is removed (Figure 2).
For educational and informational purposes only. Not financial advice. Options trading involves substantial risk of loss.
References
- Easley, D., O'Hara, M., & Srinivas, P. S. (1998). Option volume and stock prices: Evidence on where informed traders trade. Journal of Finance, 53(2), 431–465. doi.org/10.1111/0022-1082.194060
- Pan, J., & Poteshman, A. M. (2006). The information in option volume for future stock prices. Review of Financial Studies, 19(3), 871–908. doi.org/10.1093/rfs/hhj024
- Pan, J., & Poteshman, A. M. (2004). The information in option volume for future stock prices. NBER Working Paper 10925. www.nber.org/papers/w10925
- Lee, C. M. C., & Ready, M. J. (1991). Inferring trade direction from intraday data. Journal of Finance, 46(2), 733–746. doi.org/10.1111/j.1540-6261.1991.tb02683.x
- Muravyev, D. (2016). Order flow and expected option returns. Journal of Finance, 71(2), 673–708. doi.org/10.1111/jofi.12380
- The Options Clearing Corporation. Volume and open interest reports. www.theocc.com/market-data/market-data-reports/volume-and-open-interest
- Ni, S. X., Pearson, N. D., Poteshman, A. M., & White, J. (2021). Does option trading have a pervasive impact on underlying stock prices? Review of Financial Studies, 34(4), 1952–1986. doi.org/10.1093/rfs/hhaa082