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What Market Makers Actually Do

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What Market Makers Actually Do

How Do Market Makers Profit and What Is Their Role?​

Market makers are the dealers of financial markets. They stand ready to buy and sell stocks at all times, providing the liquidity that allows you to execute trades instantly without waiting for someone to take the other side. A market maker profits by buying at the bid (a slightly lower price) and selling at the ask (a slightly higher price), capturing the spread. This sounds simple, but the business is actually complex: market makers must manage inventory risk, predict price movements, and react to information in microseconds. Understanding what market makers do, how they profit, and what happens when they stop providing liquidity reveals why spreads widen during volatility and why your market orders might get worse fills than you expect.

Quick definition: Market makers are firms that continuously buy and sell securities (stocks, options, bonds) at publicly quoted prices, profiting from the bid-ask spread while providing essential liquidity to markets.

Key takeaways​

  • Market makers provide immediate execution: Without market makers, you'd have to wait for another retail trader wanting to sell before you could buy. Market makers eliminate this friction.
  • They profit from the spread: If a stock bid is $100.00 and the ask is $100.01, a market maker buys 1,000 shares at $100.00 and sells 1,000 shares at $100.01, netting $10 in profit (minus costs).
  • Inventory risk is their main challenge: Market makers are forced to hold inventory. If they buy too much stock and the price falls, they lose money. If they sell short too much and price rises, they lose money. Managing this risk is the core of their business.
  • They use information and speed to manage risk: Market makers adjust their bids and asks based on incoming order flow, volatility, and broader market signals. The better their information, the tighter they can make spreads while staying profitable.
  • They can move prices: When market makers pull their bids and asks (stop providing liquidity), spreads widen instantly. This happens during volatility spikes or when they've accumulated too much inventory. This is when retail traders get hurt.
  • HFT firms are modern market makers: Most equity market making today is done by HFT firms using algorithms. They operate at higher speeds and tighter spreads than traditional human traders.

The Bid-Ask Spread and How It Works​

Every tradeable security has two prices at any moment: the bid (what buyers will pay) and the ask (what sellers will pay). The spread between them is the market maker's potential profit on a single round-trip trade (buy and sell the same security).

Example: Apple trades with a bid of $150.00 and an ask of $150.01. The spread is $0.01. A market maker places 100 shares on the bid and 100 shares on the ask. If both orders fill, the market maker:

  • Buys 100 shares at $150.00 (cost: $15,000)
  • Sells 100 shares at $150.01 (revenue: $15,000.01)
  • Net profit: $0.01 (spread × shares)

Spread × Volume = Profit

For highly liquid stocks like Apple, spreads are tight ($0.01) because competition is fierce. Many market makers are willing to provide liquidity at tight spreads because the volume is so high they can make money through sheer volume.

For thinly traded stocks, spreads are wider. A stock trading $50 shares per day might have a $0.25 spread. The market maker makes less per share but is willing to accept it because volume is low and they need wider spreads to account for the risk of being stuck holding inventory.

Inventory Risk and Price Impact​

Here's where market making gets complicated: market makers don't just execute passive trades. They take on inventory risk, and they must actively manage it.

Imagine a market maker that decides to provide liquidity for a stock. It places a bid at $100.00 and an ask at $100.01. Now buyers and sellers arrive:

  • A buyer buys 10,000 shares at the ask ($100.01). The market maker is now long 10,000 shares.
  • A seller wants to sell 5,000 shares at the bid. The market maker buys them at $100.00.

Now the market maker is short net 5,000 shares (it owns 10,000 and has promised to deliver 5,000).

If the price drops to $99.50, the market maker has an unrealized loss:

  • 10,000 shares × ($100.01 − $99.50) = $5,100 loss on the long position
  • 5,000 shares × ($100.00 − $99.50) = $2,500 loss on the short position

The longer the market maker holds this inventory, the more risk it faces. So market makers constantly adjust their bids and asks to encourage offsetting trades.

Adjustment strategy:

  • If the market maker is long (owns more than it sold short), it widens the ask (raises the price at which it will sell), making it less attractive to buyers so it doesn't accumulate more inventory.
  • If the market maker is short (sold more than it owns), it widens the bid (lowers the price at which it will buy), making it less attractive to sellers.

This is why spreads widen during volatile or trending markets. Market makers are trying to shed inventory before prices move against them further.

Information and Speed in Market Making​

The most profitable market makers are those with the best information about supply and demand. They monitor:

  • Order flow: Are more buyers or sellers hitting the market? This informs whether the next price move is likely up or down.
  • News: Do recent tweets, earnings, economic data, or sector news suggest the stock is mispriced?
  • Cross-market signals: Do related instruments (options, bonds, related stocks) suggest this stock is cheap or expensive?
  • Time-of-day patterns: Are there regular patterns of institutional order flow at certain times?

With better information, market makers can tighten spreads and still stay profitable. If you see very tight spreads in a stock, it means market makers are confident in their ability to predict the next move. If spreads are wide, it means uncertainty—they're charging more for the risk they're taking.

Speed matters because information decays quickly. If a market maker learns that a large buyer is in the market, it can quickly adjust before that information is reflected in the public price. This is where HFT market makers have an advantage: they see information microseconds before slower traders and react instantly.

Decision tree​

Types of Market Makers​

Traditional Market Makers (mostly on options exchanges now): These are firms that stand on exchange floors (or did, historically) with explicit market-making obligations. They must provide bids and asks at all times and can't simply disappear when volatility spikes. In exchange, they get certain privileges (like priority execution or rebates). These have largely been replaced by algorithmic traders.

HFT Market Makers: These are high-frequency trading firms that provide market making through algorithms. They're faster, more sophisticated, and more profitable than traditional market makers. They dominate equity market making today. Examples include firms like Virtu Financial and Citadel Securities.

Broker-Dealers: Major banks and brokers (Goldman Sachs, Morgan Stanley, Merrill Lynch) act as market makers for their institutional clients. They maintain inventory to facilitate large block trades. They make money on spreads but also charge explicit fees.

Retail Brokers as Market Makers: Some retail brokers (like Robinhood, Webull) operate their own market-making arms or partner with market makers. This creates a potential conflict of interest: the broker profits when its customers' orders are routed to its market maker, regardless of whether the customer gets the best price.

What Happens When Market Makers Disappear​

When volatility spikes, market makers often pull their bids and asks to avoid being forced to hold inventory at terrible prices. This is when spreads widen dramatically and retail traders suffer.

Example from March 2020: During the COVID crash, stock market volatility spiked to levels not seen since 2008. Market makers pulled their quotes en masse. Spreads on major stocks like SPY widened from $0.01 to $0.10 or more. Retail traders trying to sell during the panic found very few willing buyers at reasonable prices. The market became illiquid. Retail traders were forced to sell at market and accept whatever price they could get.

This raises a key question: should market makers be required to stay active during crises? The answer is complicated. If you force market makers to stay active, they'll demand much higher spreads normally to compensate for the risk. You might get tighter spreads on normal days but wider spreads during crises. The trade-off isn't obvious.

Market Makers vs. Order Flow Payment​

Some retail brokers earn revenue by routing customer orders to market makers in exchange for payment (called "payment for order flow" or PFOF). This creates a potential conflict: the broker profits when customers' orders are routed to the highest-paying market maker, not necessarily the market maker offering the best price.

Example: You place a buy order for 100 shares of Apple through Robinhood. Robinhood routes it to Citadel Securities' market maker, which pays Robinhood $0.0001 per share ($0.01 total). Citadel fills your order at $150.02 when the public ask is $150.01. You pay $0.01 more per share ($1 total on 100 shares) to compensate Citadel for the rebate it paid Robinhood.

Is this bad? Opinions differ. Some argue it's transparent and improves retail execution (market makers compete for order flow, lowering spreads). Others argue it incentivizes worse prices for retail traders. Regulators have examined it closely. The current consensus is that it's legal but needs careful monitoring to prevent abuse.

Real-world examples​

Example 1: Apple market making during normal trading. Apple (AAPL) is the most heavily traded stock on U.S. exchanges. Dozens of market makers provide constant liquidity. The bid-ask spread is almost always $0.01 because the volume and competition are so high. A market maker might handle hundreds of thousands of shares per day, earning a fraction of a cent on each, but the total profit is significant. The market maker's strategy is mostly about speed and volume—execute billions of dollars in volume at razor-thin margins.

Example 2: Biotech stock around an FDA decision. A biotech stock awaiting FDA approval has binary risk: approval or rejection. Market makers widen spreads significantly (say, from $0.10 to $1.00) because they can't predict which way the stock will move. After the announcement, volatility drops and spreads tighten back to normal. The market maker is being paid by the spread to assume the uncertainty.

Example 3: Inventory management during a sector selloff. A market maker is heavily long biotech stocks after a good earnings season. When a negative FDA decision hits a major competitor, all biotech stocks fall. The market maker, realizing it's long too much inventory in a falling market, aggressively widens its bids (lowers the price it's willing to pay). Sellers see fewer attractive prices and pull back, reducing volume. The market maker's inventory remains stuck. This is a classic scenario where market maker interests and trader interests diverge—you want to sell, but the market maker is trying not to buy.

Common mistakes​

Mistake 1: Expecting tight spreads during low-volume periods. Market makers adjust spreads based on volatility and volume. During pre-market, after-hours, or when a stock is breaking below support, expect spreads to widen. Don't be surprised when you can't get a tight fill during volatile times—that's when market makers are managing risk, not competing for your order.

Mistake 2: Assuming all market makers provide equal liquidity. Some market makers specialize in certain stocks or order sizes. A market maker that handles thousands of Apple orders daily might be tiny and unavailable for a small-cap stock. Liquidity varies by market maker. This is why some stocks have tight spreads from many market makers (Apple) and others have wide spreads from few market makers (tiny biotechs).

Mistake 3: Trading without checking the inside market. The inside market is the best available bid and ask at any moment. When you place a limit order, you're competing with the inside market. If the inside ask is $100.01 and you place a bid for $100.00, your order won't execute. Always check the real-time bid-ask before entering an order. Many retail brokers display this poorly.

Mistake 4: Blaming market makers for every bad fill. If you place a market order during volatile trading, you might get a significantly worse price than the inside market at the moment of order. This isn't always market maker manipulation—it might be due to your order routing, your broker's latency, or general chaos. Request a full order report from your broker and analyze it before blaming market makers.

Mistake 5: Assuming payment for order flow is always bad. Some payment for order flow actually tightens spreads because it incentivizes market makers to compete for volume. The best approach: compare the actual prices you're getting across brokers and use the one with the best execution, regardless of whether it uses payment for order flow.

FAQ​

How much money do market makers make?​

It varies enormously. A major HFT market maker might profit tens of millions daily. A traditional broker-dealer market maker might clear a few million per month. The spread-based model scales with volume—more volume means more profit despite tight spreads. The largest market makers are extraordinarily profitable because they handle trillions in annual volume.

Can I become a market maker?​

As a retail trader, not really. Market making requires capital (millions to billions), specialized technology, regulatory approval, and exchange memberships. Some brokers like Interactive Brokers offer "option market making" where retail traders can provide two-sided quotes on options with capital requirements of tens of thousands. But equities market making is dominated by large firms with serious resources.

Why are options spreads wider than stock spreads?​

Options are less liquid than the underlying stock, so market makers require wider spreads to compensate for inventory risk. Additionally, options pricing is more complex—market makers must estimate volatility, delta, gamma, and other factors to price them correctly. A small error in volatility estimation can result in a large loss. The wider spread compensates for this model risk.

What happens if a market maker fails to deliver?​

Market makers are required to settle trades (deliver shares or cash) by T+2 (two days after trade date). If a market maker fails to deliver, it's a regulatory violation subject to fines and enforcement action. The financial penalty from fines and operational costs usually exceeds any profit from not delivering, so market makers avoid this. Fails are rare for major market makers.

Do market makers ever lose money?​

All the time. On volatile days, market makers might accumulate inventory at bad prices and end up long a stock that crashes or short a stock that soars. The best market makers design their strategies to minimize losses, but losses are inevitable. Over long periods, profits outweigh losses, but daily and weekly losses are normal.

Is the bid-ask spread unfair to retail traders?​

No more than it is to institutional traders. Everyone pays the spread. The difference is that institutions trade larger sizes and can negotiate tighter spreads (sometimes penny spreads or better), while retail traders get the quoted spreads. If you want tighter spreads, use a professional trader's broker like Interactive Brokers.

How do market makers predict the next price move?​

They use a combination of historical data (price patterns, volatility trends), current information (order flow, news, related instruments), and statistical models. A sophisticated market maker might have models predicting the probability of an up move or down move in the next second based on the current bid-ask, recent volume, and broader market trends. These models are proprietary and vary by firm.

Summary​

Market makers are essential infrastructure for liquid financial markets. They profit by buying at the bid and selling at the ask, but the real business is managing inventory risk and predicting price movements. Market makers with better information, faster technology, and more capital are more profitable. When you place an order, a market maker fills it, and its decisions about bid-ask spreads reflect its view of the stock's future direction and its current inventory. Understanding market maker behavior—why spreads widen during volatility, how they manage inventory, what signals they respond to—helps you make better trading decisions and avoid chasing their fills during the worst times.

Next​

Do Retail Traders Have an Advantage?