Arbitrageur

An arbitrageur is a type of investor who attempts to profit from price inefficiencies in the market by making simultaneous trades that offset each other to capture risk-free profits. An arbitrageur would, for example, seek out price discrepancies between stocks listed on more than one exchange by buying the undervalued shares on one exchange while short selling the same number of overvalued shares on another exchange, thus capturing risk-free profits as the prices on the two exchanges converge.

Arbitrageurs are typically very experienced investors since arbitrage opportunities are difficult to find and require relatively fast trading. Arbitrageurs also play an important role in the operation of capital markets, as their efforts in exploiting price inefficiencies keep prices more accurate than they otherwise would be.

As a simple example of what an arbitrageur would do, consider the following. The stock of Company X is trading at $20 on the New York Stock Exchange (NYSE) while, at the same moment, it is trading for the equivalent of $20.05 on the London Stock Exchange (LSE). A trader can buy the stock on the NYSE an immediately sell the same shares on the LSE, earning a total profit of 5 cents per share, less any trading costs. The trader exploits the arbitrage opportunity until the specialists on the NYSE run out of inventory of Company X's stock, or until the specialists on the NYSE or LSE adjust their prices to wipe out the opportunity.