Market Maker

A market maker is a dealer that holds itself out as willing to buy and sell a security for its own account on a regular or continuous basis. The definition is in the Securities Exchange Act, at 15 U.S.C. 78c(a)(38), and it is worth reading as the three separate limbs it actually has: the term "means any specialist permitted to act as a dealer, any dealer acting in the capacity of block positioner, and any dealer who, with respect to a security, holds himself out (by entering quotations in an inter-dealer communications system or otherwise) as being willing to buy and sell such security for his own account on a regular or continuous basis."

The third limb is the one people mean, and its operative words are "buy and sell" and "regular or continuous". Anybody can be willing to buy a security, and anybody can be willing to sell one. A market maker is willing to do both at the same time, repeatedly, which is what allows an investor to trade at a moment of their own choosing rather than waiting for someone with the exact opposite intention to appear. It does that as principal, taking the position onto its own books. The compensation for the service, the gap between the price at which it will buy and the price at which it will sell, is covered on the bid-ask spread page.

Regulation NMS splits the statutory category into two species, and the line is where the dealing happens. An "exchange market maker", at 17 CFR 242.600(b)(37), is "any member of a national securities exchange that is registered as a specialist or market maker pursuant to the rules of such exchange" — a status granted by a venue, with the obligations that venue's rulebook attaches. An "OTC market maker", at (b)(75), is "any dealer that holds itself out as being willing to buy from and sell to its customers, or others, in the United States, an NMS stock for its own account on a regular or continuous basis otherwise than on a national securities exchange in amounts of less than block size." Note the two qualifiers in that second definition. It happens away from an exchange, and it is about ordinary-sized trades rather than blocks.

That block-size qualifier connects back to the statute's forgotten middle limb. "Block size" is defined at (b)(17) as an order "of at least 10,000 shares" or "for a quantity of stock having a market value of at least $200,000" — a disjunctive test, so either one suffices. Those figures are fixed by the rule rather than adjusted annually. Negotiating a large block is a different activity from quoting ordinary sizes all day, and the statute handles it separately: a dealer "acting in the capacity of block positioner" is a market maker under its own limb, without needing the continuous two-sided quoting the third limb describes.

The rules treat a market maker as market infrastructure, not merely as a trader. A market maker is one of the entities Regulation NMS calls a "market center", defined at (b)(55) as "any exchange market maker, OTC market maker, alternative trading system, national securities exchange, or national securities association", and it is also a "trading center" under (b)(106), which reaches any broker or dealer that executes orders internally by trading as principal or crossing orders as agent. Those are not honorific labels. Being a market center is what pulls a firm into obligations that ordinary brokers escape, including the monthly order-execution reporting a broker that is not a market center only owes above a customer-account threshold.

The vocabulary of the rules presumes a firm that publishes and then revises. Regulation NMS defines a "revised bid or offer" at (b)(91) as "a market maker's bid or offer which supersedes its published bid or published offer", and a "revised quotation size" at (b)(92) as "a market maker's quotation size which supersedes its published quotation size". Both definitions exist only because the assumed behavior is a standing published quotation that gets updated, which is the continuous-basis requirement seen from the market-data side. And a quotation is legally firm for at least a round lot, which is what makes a published quote something an investor can act on rather than an invitation to negotiate.

Where a market maker's economics come from, in one sentence, because the argument belongs elsewhere. The firm buys at its bid and sells at its offer, and the difference is its compensation for standing ready and for holding inventory that can move against it; the bid-ask spread page covers that in full, and the reasons a quote widens when the firm suspects the person trading with it knows more than it does are covered on the adverse selection page. For retail equity orders in particular, the firm on the other side is often an off-exchange dealer that the broker routed the order to rather than an exchange, and the economics of that arrangement have their own page.

An automated market maker is a different thing that happens to share the words. In decentralized crypto venues, an automated market maker is a smart-contract formula that prices a swap against a pool of reserves. There is no dealer, no firm holding itself out to anyone, no published quotation and no obligation to deal, so nothing in 15 U.S.C. 78c(a)(38) reaches it. The decentralized exchange page covers how that design actually prices a trade.

The firm publishes a bid and an offer with sizes attached, updates them as conditions change, and takes the other side of orders that arrive. Buying at its bid and selling at its offer, it accumulates a position in one direction or the other and manages the resulting exposure. On an exchange the firm is registered as a market maker under that exchange's rules and takes on whatever quoting obligations they impose. Off-exchange, the status follows from the conduct: a dealer that holds itself out as willing to buy from and sell to others in an NMS stock, for its own account, on a regular or continuous basis, and in amounts below block size, is an OTC market maker whether or not it has applied to be anything.

A hypothetical illustration of the block-size boundary, since the OTC definition is written in terms of it. Block size is met by an order of at least 10,000 shares or one with a market value of at least $200,000, and either limb is enough. So an order for 10,000 shares of a $12 stock is worth 10,000 × $12 = $120,000, which fails the dollar test but satisfies the share test, and is block size. An order for 5,000 shares of a $50 stock is worth 5,000 × $50 = $250,000, which fails the share test but satisfies the dollar test, and is also block size. An order for 5,000 shares of the $12 stock is worth 5,000 × $12 = $60,000 and satisfies neither, so it is not block size. Only the third of those is inside the OTC market maker definition's "amounts of less than block size"; the first two are the territory the statute's block positioner limb addresses. Working through it that way makes clear that the category is about the everyday flow rather than about the largest trades.

What the function does for an investor

• It makes trading possible at a moment of the investor's choosing, rather than only when someone with the exact opposite intention shows up.
• Its published quotations are firm for at least a round lot, so the price on the screen is something that can be acted on.
• Because the firm quotes continuously, the market has a visible price even in a security nobody happens to be trading at that instant.
• Competition between firms willing to quote both sides is what narrows the gap between the two prices.

The honest limits

• The service is not free: the investor crossing the gap between the bid and the offer is paying for it, and the cost is embedded in the price rather than itemized.
• A market maker is not obliged to be generous, and the gap it quotes widens when the security is hard to value or hedge, which is when an investor is most likely to want to trade.
• Off-exchange market making is defined by conduct rather than by registration, so an investor's counterparty may be a firm they have never heard of and did not choose.
• The category is written around ordinary trade sizes; a genuinely large order is a different negotiation, handled under a different limb of the statute.