Strategy
Market Making: Quote Skew, Inventory Risk, Capital Efficiency
Market making earns the bid-ask spread in exchange for inventory and adverse-selection risk. The job is not quoting — it's managing inventory and fading adverse selection.
Market making posts simultaneous bid and ask quotes and earns the spread when both sides fill. The job is not the quoting — quoting is mechanical. The job is managing inventory and fading adverse selection.
The two real risks
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Inventory risk. Every fill leaves you holding (or short) a position. Holding inventory means market exposure, and market makers do not want directional exposure. Inventory must be unwound, ideally by being filled on the opposite side at the spread.
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Adverse selection. Every counterparty trading against your quote knows something you don't, or the trade wouldn't happen. The fast money picks off your quote when news is moving the price; the slow money trades against you because they need liquidity. The first costs you money; the second pays you the spread. The job is filtering one from the other.
Quote skew
The market maker's primary control is skew — pricing the bid further from the mid than the ask, or vice versa, to encourage fills on the side that reduces inventory.
bid = mid − k × spread − γ × inventory
ask = mid + k × spread − γ × inventory
When inventory is long, both quotes shift down: encourages a sell to the offer (reduces long), discourages a buy from the bid. γ is the inventory-aversion parameter.
Capital efficiency
Market making is a capital-light strategy in expected terms but capital-intensive in worst-case terms. Daily P&L can be flat for months and then take a meaningful hit on a single dislocation event. Required capital is sized to the tail risk of inventory at moments of liquidity withdrawal, not to expected risk.
Failure modes
- Latency disadvantage. If you can't cancel quotes faster than the fastest informed traders can fill them, you lose to adverse selection on every news print.
- Toxic flow concentration. Operating in a market where the dominant counterparty is informed (e.g., institutional flow on a retail-flow venue) is structurally losing.
- Liquidity withdrawal events. When everyone pulls quotes simultaneously, your remaining quotes are filled at terrible prices.
Why most retail market making fails
The infrastructure cost of competitive market making — co-location, exchange fees, low-latency data — is fixed. Retail-scale operations cannot amortize it. Without that infrastructure, you are systematically the slowest market maker on the venue, which means you fill only when you're wrong.