Arbitrage

Arbitrage means exploiting a price gap by taking offsetting positions at the same moment, buying in one market while selling in another, or borrowing on one side while lending on the other, in assets that are identical or economically interchangeable. In its pure textbook form arbitrage requires no net investment and carries no risk: the trader locks in a gain because both sides of the trade are executed at once.

Arbitrage plays an important role in markets because it enforces consistency between prices. When traders buy where an asset is cheap and sell where it is dear, they push the two prices together. The principle that identical assets should trade at the same price, the law of one price, depends on arbitrage to hold in practice.

An arbitrage opportunity exists whenever the same economic exposure can be bought for less in one place than it can be sold for in another, after costs. The trader buys the cheap version, sells the expensive version, and delivers one against the other. The profit is the price difference minus transaction costs, financing costs and taxes. In liquid markets such opportunities are small and disappear quickly, so they are mostly captured by banks, market makers and automated trading firms with low costs and fast execution.

Spatial arbitrage

Buying an asset in one market and selling it in another, such as gold in two cities or a share listed on two exchanges. Transport, settlement and regulatory barriers determine how large the gap can grow.

Triangular currency arbitrage

A form of currency arbitrage that exploits inconsistencies among three exchange rates. If EUR/USD trades at 1.1000 and USD/JPY at 150.00, the implied EUR/JPY cross rate is 165.00. If a dealer quotes EUR/JPY at 166.00, a trader can sell euros for yen at 166.00, convert the yen to dollars at 150.00 and the dollars back to euros at 1.1000. Starting with EUR 1 million, this returns about EUR 1,006,061 before costs, a gain of roughly 61 basis points.

Covered interest arbitrage

This links the spot rate, the forward rate and the interest rates of two currencies. If the forward premium does not match the interest differential, a trader can borrow in one currency, convert, invest in the other and hedge back with a forward. Persistent deviations from this relationship since 2008 are measured as the cross-currency basis.

Cash-and-carry and statistical arbitrage

Cash-and-carry trades buy an asset and sell a futures contract on it when the futures price exceeds the spot price plus carrying costs. Statistical arbitrage, by contrast, relies on historical relationships between prices and is not risk-free, despite the name.

Arbitrage also explains phenomena outside trading desks. Where capital controls prevent free conversion, onshore and offshore prices for the same currency can diverge, as in the CNY-CNH spread, or a parallel market rate can emerge. Premiums on stablecoins in P2P trading markets in countries with restricted access to dollars reflect the same forces. In licensing, regulatory arbitrage refers to choosing a jurisdiction or structure because its rules are cheaper to satisfy, which is a separate but related use of the word.

Real arbitrage is rarely riskless. Execution risk arises when one leg fills and the other does not; settlement risk arises when one side delivers and the other defaults. Capital requirements, margin and haircuts limit how much can be deployed. Economists Andrei Shleifer and Robert Vishny described these constraints in their 1997 paper on the limits of arbitrage, showing that mispricings can widen before they close and force arbitrageurs to exit at a loss. The 1998 collapse of the hedge fund Long-Term Capital Management, whose strategies relied on spreads converging, is a frequently cited illustration. Where controls or legal barriers block one leg of the trade entirely, prices can stay apart indefinitely.