Arbitrageur

What Is an Arbitrageur?

An arbitrageur is an investor or trader who seeks to profit from a price difference between the same asset, or closely related assets, in different markets or forms. The strategy involves buying the lower-priced version and selling the higher-priced one at nearly the same time, so the gain is locked in regardless of which way the broader market moves. Arbitrageurs are often said to help prices converge, because their trading pushes prices toward alignment.

How Arbitrage Works

Price gaps can appear for several reasons. The same stock may trade on two exchanges, a company's shares and its convertible bond may be priced inconsistently, or a pending acquisition may leave the target's share price slightly below the offer price. An arbitrageur buys the cheaper position and sells the more expensive one. Because the trades offset each other, the profit is ideally the spread between the prices, minus costs such as transaction costs and financing.

In theory, pure arbitrage is riskless. In practice, it carries risk. Prices can move further apart before they converge, trades may not execute at the expected prices, and deals can fall apart. Arbitrage that focuses on announced takeovers is often called merger arbitrage.

Why It Matters to Investors

Arbitrageurs help keep markets consistent. Their activity narrows pricing gaps, which helps related securities stay aligned with one another. This supports the idea of a efficient market in which obvious mispricings are corrected quickly. For individual investors, the practical lesson is that small mispricings tend to be found and removed by professional traders with fast execution, low costs, and access to large amounts of capital. Profits per trade are typically small, so these opportunities are generally difficult for individuals to capture.

Advantages and Disadvantages

• Returns may depend less on the overall direction of the market
• Trading activity can help narrow price differences across markets
• Profits are usually small and depend heavily on precise execution
• Risks include deal failure, financing costs, and prices moving against the position