Two Survival Structures of Market Makers and Arbitrageurs
Market makers and arbitrageurs represent two distinct survival structures in high-frequency trading. Market makers primarily use limit orders (makers) to profit from the bid-ask spread, enjoying high capital efficiency (nominally 100%) but bearing inventory risk. This "inventory risk" arises from passive, fragmented, and discontinuous order fills in the limit order book (LOB). This risk, while a potential cost, can also contribute to excess profit if managed within control boundaries, allowing for mean reversion. Market makers essentially sell "time" (uncertainty over execution timing) to the market for price control and low fees.
In contrast, cross-exchange arbitrageurs typically use market orders (takers) to exploit price differences or funding rates, resulting in lower nominal capital efficiency (requiring capital on both exchanges) and higher transaction costs. Their risk exposure stems from asymmetries in exchange rules (e.g., minimum order sizes), execution latency, and infrastructure risks (e.g., ADL, oracle drift). These exposures are active, exogenous gaps that primarily erode profits rather than contribute to them. Arbitrageurs essentially sell "space" (capital sunk across venues) for localized, immediate certainty.
Both strategies engage in a trade-off between execution friction and residual risk. Optimal systems allow for temporary, controlled risk exposure rather than enforcing zero exposure at all costs. Their evolution converges towards hybrid models: arbitrageurs may use maker orders to reduce costs, while market makers may use taker orders or hedges for risk management. Ultimately, both use different forms of risk exposure—market makers exposing inventory, arbitrageurs immobilizing capital—to extract marginal, hard-won certainty from the market.
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