Quick Answer
The NYSE assigns exactly one Designated Market Maker (DMM) to each listed security. The DMM must step in and trade when public liquidity runs short (affirmative obligation) but step back when it doesn't (negative obligation), and can act as either agent or principal, but never both in the same trade.
The DMM is the mechanism that makes the NYSE's auction model work: a single accountable party responsible for keeping trading orderly in its assigned stocks.
Role and Function of the DMM
- Formerly known as specialists, DMMs are assigned to specific securities on the NYSE
- Each listed security has one DMM responsible for maintaining a fair and orderly market
- DMMs operate both manually and electronically to facilitate price discovery
- DMMs must quote at the NBBO (National Best Bid and Offer) a specified percentage of the time
Remember: One security = one DMM on the NYSE. This is a fundamental structural difference from Nasdaq, which has multiple competing market makers per stock.
Listing requirements: a security must meet the exchange's listing standards (financial thresholds, minimum shareholder counts, and similar criteria) before it can be assigned a DMM at all.
DMM Obligations
DMMs have five core obligations under NYSE requirements:
| Obligation | Description |
|---|---|
| Maintain fair and orderly market | Must provide continuous two-sided quotes (bid and offer) in assigned securities |
| Facilitate price discovery | Particularly important during market openings, closings, and periods of significant imbalance |
| Provide liquidity | Must commit their own capital to buy or sell when there is insufficient public interest |
| Minimize price volatility | Must trade to dampen excessive price swings, not to amplify them |
| Manage the auction | Facilitate opening and closing auctions on the NYSE |
The Dual Obligation: Affirmative and Negative
This is one of the most-tested concepts in this unit. DMMs have two opposing obligations:
- Affirmative obligation: The DMM must step in and trade when needed to maintain a fair and orderly market: buying when no one else is buying, selling when no one else is selling
- Negative obligation: The DMM must step back when the public market is functioning well; the DMM should NOT trade for its own account when there are sufficient public orders
Think of it this way: The DMM is the "buyer for every seller and seller for every buyer" in its assigned stocks. When public order flow dries up on one side, the DMM steps in to fill that gap. When there is plenty of natural public interest, the DMM stays out.
Exam Tip: Gotchas
A DMM should NOT trade for its own account when there are sufficient public orders to maintain an orderly market. The affirmative obligation kicks in only when public liquidity is insufficient. If the exam describes a DMM trading actively when there is plenty of public interest, that violates the negative obligation.
Principal vs. Agency Transactions
DMMs can act in two capacities:
- Principal transaction: The DMM buys or sells from its own inventory (acting as dealer)
- Must disclose principal capacity on the trade confirmation
- Trades as principal to fill gaps in supply or demand
- Agency transaction: The DMM executes a customer order against another order on the book (acting as broker)
- Earns a commission for agency trades
Key rule: A DMM cannot act as both agent and principal in the same transaction.
Exam Tip: Gotchas
A DMM cannot be agent AND principal in the same trade. Principal trades require disclosure on the trade confirmation; agency trades earn a commission. If the exam asks about a DMM filling a customer order from its own inventory while also earning a commission on the same trade, that is a violation.
NYSE DMM Conduct Requirements
The core NYSE conduct requirements governing DMM behavior:
- DMMs must maintain a fair and orderly market in each security in which they are registered
- DMMs must maintain depth by dynamically adding liquidity when insufficient public liquidity exists
- DMMs have affirmative obligations to trade against the prevailing trend when necessary to reduce volatility
- DMMs have negative obligations not to trade for their own account when sufficient public interest exists
Exam Tip: Gotchas
The affirmative obligation means trading AGAINST the trend (buying on declines, selling on rallies), not going with the trend. When public interest is insufficient, the DMM steps in as principal; when public interest returns, the negative obligation requires the DMM to step back.
SEC Order Handling Rules
- A market maker must display a customer limit order that would improve its own quote (narrow the spread)
- Applies to NMS (National Market System) securities
- Designed so a customer's limit order gets the benefit of best execution instead of being absorbed silently into the market maker's own quote
Exam Tip: Gotchas
If a customer's limit order would narrow the market maker's quoted spread, the market maker must either execute it or display it. The market maker cannot simply ignore a limit order that would improve the market.
What Should You Check on Exam Day?
- Can you distinguish the affirmative obligation (step in when liquidity is thin) from the negative obligation (step back when it isn't)?
- Do you know a DMM can act as agent or principal, but never both on the same trade?
- Can you identify a principal DMM trade (needs confirmation disclosure) versus an agency DMM trade (earns a commission)?
- Do you know when a market maker must display a customer's limit order under the SEC order handling rules?