Arbitrage

The core idea is simple: if gold is quoted at a hypothetical $1,900 per troy ounce in London and $1,905 in New York at the exact same moment, a trader could theoretically buy in London and sell in New York, pocketing a $5 difference. That gap is the arbitrage opportunity. In practice, transaction costs, currency conversion, and execution speed usually eat into or eliminate the profit, which is why professional arbitrageurs invest heavily in fast technology.

Arbitrage is sometimes called a "riskless profit," but that label requires a caveat. True riskless arbitrage — where both legs of the trade execute simultaneously and at locked-in prices — is rare. More commonly, traders face execution risk: the price in one market moves before the second trade goes through. This is sometimes called "legging risk," because one leg of the trade is exposed.

Arbitrage plays a crucial role in keeping markets efficient. When a price gap opens, arbitrageurs pile in, buying the cheaper version and selling the more expensive one. Their collective activity pushes the cheaper price up and the more expensive price down until the gap closes. This is why identical assets rarely trade at dramatically different prices for long across liquid markets.

Arbitrage also appears in spot versus futures pricing. If a futures contract trades far above the spot price in a way that cannot be explained by carrying costs (storage, interest, insurance), arbitrageurs will buy the spot asset and sell the futures contract, pressing the two prices back toward alignment. Understanding this mechanic is central to reading contango and backwardation in commodity markets.