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Key Takeaways
- Auction order imbalance is unmatched eligible quantity at a specified price.
- Buy interest above sell interest creates a buy imbalance; the reverse creates a sell imbalance.
- Paired quantity is the share quantity the two sides can match.
- The worked auction pairs 275,000 shares and leaves a 75,000-share sell imbalance.
- Read direction, paired quantity and indicative price together, then reconcile the final match.
What is an order imbalance?
An order imbalance is the excess eligible buy or sell quantity left unpaired at a specified price in an auction or other matching process. More buying than selling produces a buy imbalance; more selling than buying produces a sell imbalance. Exchanges publish these quantities during opening, closing and other auctions, and traders read them alongside the indicative price and paired shares to understand the auction’s order pool.
How is an order imbalance calculated?
Net order imbalance equals eligible buy quantity minus eligible sell quantity at the measured price; a positive result is a buy imbalance and a negative result is a sell imbalance. At $72.25, the example has 275,000 eligible buy shares and 350,000 eligible sell shares. Subtracting sells from buys gives −75,000 shares, indicating a sell imbalance.
The two sides can pair 275,000 shares. At $72.25, that matched quantity represents $19,868,750.
The combined eligible interest is 625,000 shares. The 75,000-share excess is 12% of that combined quantity. Read the three together: 275,000 shares pair at $72.25, and 75,000 shares of selling still need a buyer.
Formula
Net order imbalance = eligible buy quantity − eligible sell quantity- A positive result is a buy imbalance; a negative result is a sell imbalance.
- Paired quantity equals the smaller of eligible buy and sell quantities at the measured price.
Worked Example
An auction update at a $72.25 reference price shows 275,000 eligible buy shares and 350,000 eligible sell shares.
- Net imbalance: 275,000 − 350,000 = −75,000 shares
- Direction: negative means a 75,000-share sell imbalance
- Paired quantity: min(275,000, 350,000) = 275,000 shares
- Sell imbalance as a share of total eligible interest: 75,000 / 625,000 × 100% = 12%
At $72.25, the eligible sides pair 275,000 shares for $19,868,750. The remaining 75,000 shares are on the sell side. That excess is 12% of the combined 625,000-share eligible interest.
How to read imbalance, paired shares and indicative price
The indicative price identifies the candidate match price. Paired shares identify the matched quantity at that price, and imbalance identifies the excess side.
Exchanges also distinguish order subsets, including market-order and total imbalance fields. The eligible order instructions, candidate price and exchange matching rules determine the calculation.
As interest enters, changes or executes, the auction state advances. The final print supplies the actual match price and quantity.
Compare auction quantities with the stock’s normal auction volume and market depth. Then read the completed price and size in time and sales. Options traders pair the imbalance with options flow, which shows the contracts traded into the auction, and with the options profit calculator, which prices the position from the final match price.
Limitations of order imbalance data
- Each imbalance message is the order pool at its publication time. Interest keeps entering, changing and executing until the auction runs, so take the final match price and quantity from the completed auction.
- Check which field you are reading: the market-order imbalance and the total imbalance count different sets of orders for the same stock.
- Scale the imbalance to the stock’s normal auction volume. A 75,000-share imbalance means more in a stock with small auctions than in one with large auctions.
- Matching rules, order eligibility and publication times differ by exchange, so read each venue’s field definitions before comparing imbalances across exchanges.
Bottom line
An order imbalance shows how much eligible interest an auction cannot yet pair and on which side. Read it with paired shares and the indicative price, compare its size with normal auction volume, and take the outcome from the final print rather than the last indication.
Clear answers
Frequently Asked Questions
Sources and Further Reading
- Nasdaq: Opening and Closing Crosses
- NYSE: Auctions and Imbalance Publication Information
- Cboe: Titanium U.S. Equities Auction Process
How entries are sourced, calculated and updated: editorial methodology.