Arbitrageur

A trader who exploits price inconsistencies across markets or instruments, pushing prices toward the law of one price (subject to real-world frictions).
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In one sentence

An arbitrageur tries to profit from mispricing across related assets or markets, helping enforce the law of one price—though “risk-free” arbitrage is rare once costs and execution risk are included.

What arbitrage looks like

The core idea is buy the cheap claim, sell the expensive claim when both represent (nearly) the same payoff.

Common forms:

  • Spatial arbitrage: same asset priced differently across venues (after fees/latency).
  • Cash-and-carry: spot vs futures mispricing for storable commodities.
  • Covered interest parity (FX): spot, forward, and interest rates linked by no-arbitrage.
  • Convertible/statistical arbitrage: exploit relative mispricing with hedges (often not risk-free).
    flowchart LR
	  A["Mispricing detected"] --> B["Buy underpriced leg"]
	  A --> C["Sell overpriced leg"]
	  B --> D["Hedge / lock payoff"]
	  C --> D
	  D --> E["Mispricing narrows"]
	  E --> F["Profit after costs<br/>(if execution succeeds)"]

Limits to arbitrage (why mispricing can persist)

Even when a trade looks like “free money,” real frictions matter:

  • transaction costs (fees, bid–ask spreads),
  • funding and margin constraints (capital tied up, margin calls),
  • model risk (the “cheap” leg may not be comparable),
  • timing/execution risk (prices move before both legs are filled),
  • short-sale constraints (can’t short the overpriced asset).

These frictions are why arbitrage is closely tied to the idea of “limits to arbitrage” in asset pricing.

  • Law of One Price: Identical payoffs should have (nearly) the same price across markets once costs are included.
  • Hedger: A trader who uses positions to reduce exposure to risk.
  • Speculator: A trader who takes directional risk to profit from price movements.
  • Limits to Arbitrage: Constraints that prevent mispricing from being fully eliminated.
  • Market Efficiency: The idea that prices incorporate information; arbitrage is a key mechanism supporting this.

Quiz

### What is the primary goal of an arbitrageur? - [x] Profit from mispricing by buying cheap and selling expensive claims - [ ] Predict future price movements - [ ] Provide liquidity to markets - [ ] Hedge against potential losses > **Explanation:** In theory arbitrage is “risk-free,” but in practice profits are after costs and subject to execution and funding risk. ### What does the term "arbitrageur" originate from? - [ ] The Latin word "arbitrum" - [x] The French word "arbitrer" - [ ] The German word "arbiter" - [ ] The Greek word "arbitrazo" > **Explanation:** The term "arbitrageur" is derived from the French word "arbitrer," which means "to judge" or "to arbitrate." ### In which strategy does an arbitrageur buy an asset in one market and simultaneously sell it in another market? - [x] Arbitrage - [ ] Speculation - [ ] Hedging - [ ] Market making > **Explanation:** Arbitrage involves buying and simultaneously selling an asset in different markets to profit from the price differential. ### How do arbitrageurs contribute to market efficiency? - [ ] They predict future price movements - [ ] They hold onto assets for long terms - [x] They narrow price differentials across markets - [ ] They provide advisory services > **Explanation:** By exploiting price discrepancies, arbitrageurs help equalize prices across markets, making them more efficient. ### Who assumes greater risk, an arbitrageur or a speculator? - [ ] Arbitrageur - [x] Speculator - [ ] Neither - [ ] Both equally > **Explanation:** A speculator predicts future market movements and assumes greater risk compared to an arbitrageur who relies on simultaneous transactions to minimize risk. ### An arbitrageur typically executes transactions: - [ ] After a long research period - [x] Simultaneously - [ ] Sequentially with delays - [ ] Based on forecasts > **Explanation:** The goal is to reduce exposure to price movements between legs of the trade. ### Which of the following is NOT a common arbitrage strategy? - [x] Portfolio balancing - [ ] Risk arbitrage - [ ] Convertible arbitrage - [ ] Statistical arbitrage > **Explanation:** Portfolio balancing is not a form of arbitrage; it is a strategy for managing investment risk. ### True or False: Arbitrageurs help in price discovery. - [x] True - [ ] False > **Explanation:** Through their trades, arbitrageurs help adjust prices so they reflect true market value, aiding in price discovery. ### What role do algorithms play in modern arbitrage? - [ ] They decrease market efficiency - [x] They detect price discrepancies quickly - [ ] They make long-term forecasts - [ ] None of the above > **Explanation:** Algorithms enable rapid detection of price discrepancies, allowing arbitrageurs to exploit these opportunities efficiently. ### Which market is least likely to provide arbitrage opportunities? - [ ] Forex - [ ] Commodity Markets - [ ] Cryptocurrency Exchanges - [x] Perfectly Efficient Markets > **Explanation:** In perfectly efficient markets, all available information is reflected in prices, making arbitrage opportunities rare or non-existent.
Arbitration
Arbitrage Pricing Theory