What Are Market Makers?
A market maker is a firm that continuously quotes both a buy price and a sell price in a security, standing ready to trade either way. The spread between those two quotes is the compensation, and the inventory left over at the end of the day is the risk being paid for.
How it works
A market maker posts two prices at once: one they will buy at and one they will sell at. Both are live, both are for a stated size, and both are updated continuously through the session.
The obligation is the point. A retail trader quotes nothing and waits for a setup. A market maker is committed to being on both sides whether the moment is attractive or not, and that commitment is what makes a market continuous rather than sporadic.
Their revenue is the spread. Buy at the bid from someone who wants out, sell at the ask to someone who wants in, and the difference is earned without any view on direction.
On the site’s shared history that spread measures 2% of a typical bar’s range. Multiply a small number by an enormous count of trades and you have the business model.
The inventory problem
In practice they are the resting orders in the order book. When a market order fills instantly at a good price, the thing it filled against is very often a market maker’s quote rather than another retail trader.
That is worth stating plainly because it changes how the market feels. There is rarely a person on the other side of your trade who wanted the opposite thing. There is usually a firm whose business is to take the other side of anything.
The risk is inventory. Having bought from sellers all morning, a market maker is long a position they did not choose, and the price can keep falling while they hold it.
That is the actual danger in the business, and it is why quoting is not free money. The spread is compensation for being obliged to accumulate exactly what everyone else is trying to get rid of.
Inventory gets hedged rather than held. A firm long shares from customer flow will typically offset that exposure elsewhere — in a correlated instrument, an index, or an option — which is how activity in one market propagates into another.
In practice: a morning of quoting
Work through a morning. A market maker quotes 99.98 bid, 100.02 ask. Sellers hit the bid all morning; the firm accumulates 40,000 shares at an average of 99.98 and has earned nothing yet, because the spread is only realised when the position is unwound.
If buyers arrive in the afternoon, those shares go out at 100.02 and the firm has earned four cents a share for providing continuous liquidity. If instead the price falls to 99.50, the four cents is irrelevant and the inventory is the whole story.
Quote width tracks uncertainty. When the next price is hard to predict, the risk of being filled just before a large move rises, and the quote widens to compensate. The widening is a measurement of uncertainty rather than a punishment.
This is also why volume overstates conviction. A large share of reported volume is intermediation: the same position passing through a firm on its way from one participant to another, counted at each step.
When it fails
The failure mode from a trader’s seat is reliability at the wrong moment. Quotes are tightest when conditions are calm and cheap to trade, and widest during news, at the open, and around halts. Exactly when you most want to transact, the cost of doing so is highest.
There is no obligation to maintain a tight quote. A designated market maker on a listed venue has duties around continuous quoting, but those duties do not amount to a promise about width. The width is a business decision remade continuously.
And an electronic market maker can step back entirely. In genuinely disorderly conditions, quoting becomes uneconomic, quotes thin out, and the depth that made a symbol feel liquid all year is not there on the one day it mattered.
The second failure is on the trader’s side rather than theirs. Judging a symbol’s liquidity from its quote on a calm afternoon produces a number that does not survive contact with news. Liquidity is a condition, not a property of the instrument, and a market maker’s willingness to quote is the thing that changes.
A third misreading is treating quote movement as a forecast. A quote that steps down before price falls looks like foreknowledge and is usually inventory management: a firm already long from customer selling lowers where it is willing to buy more. The sequence is real; the causation runs the other way from how it appears.
The practical response to all three is the same and it is unglamorous. Trade the liquid part of the session where you can, size to the depth that is actually showing rather than the depth you saw yesterday, and treat a suddenly wide quote as information about conditions rather than an invitation to push through it.
The original data
63 of the 24,971 videos measured for this site cover market makers, at a median of 20,412 views. That is one of the higher counts in the market-mechanics group, and much of that coverage frames the role adversarially.
The framing this page uses instead is indifference. A market maker profits from the spread regardless of which way the price then goes, and hedges away the direction. That is not a claim that the arrangement is fair to you — the spread is a real cost you pay — but it does mean the quote is not aimed at you personally.
Related
The bid-ask spread is the fee this business earns. The order book is where their quotes rest. And payment for order flow is the arrangement by which retail orders reach them without ever touching an exchange.
The most useful thing I ever learned about market makers is that they are not trying to beat me. They are trying to end the day flat. Once I stopped reading their quotes as opinions, a lot of what happens around the open stopped being mysterious.
— Michael Whitman
This page is educational, not financial advice. Test every idea on your own charts before risking money.