Arbitrage

Arbitrage is a financial practice used to profit from price differences. It occurs when the same asset or similar assets trade at different prices in different markets. An arbitrageur is a person or entity that seeks out these discrepancies. By buying low in one market and selling high in another, they capture the difference as profit. This process has a major effect on the global economy. It helps cause prices to converge, which means they move closer together until they are nearly the same.

In academic economics, arbitrage is defined very strictly. A true arbitrage is a transaction that involves no negative cash flow. This means the person performing the trade is guaranteed not to lose money at any point. It must also result in a positive cash flow in at least one possible state. In simple terms, it is the possibility of a risk-free profit after all transaction costs are paid. However, in common use, the term is often applied more broadly. For example, statistical arbitrage refers to expected profits where losses are still possible.

To achieve a risk-free profit, the transactions must happen simultaneously. If a trader buys an asset but cannot sell it immediately, they face market risk. This is the danger that prices might change before the second part of the trade is finished. This specific problem is known as execution risk or leg risk. In modern markets, this is usually only possible with electronic securities. Even then, prices can move in the split second between the two trades. Because of these dangers, many traders face small losses from failed executions.

There are specific conditions that allow arbitrage to take place. First, the same asset must not trade at the same price on all markets. This is often called the law of one price. Second, two different assets with identical cash flows must not trade at different prices. Third, an asset with a known future price should trade at its discounted present value. This includes things like grain, which has significant storage costs. If these conditions are not met, an arbitrage opportunity exists.

One complex application of these ideas is arbitrage-free pricing for bonds. A bond is a financial instrument that pays money, called coupons, over a period of time. Instead of using one single discount rate, experts use multiple discount rates. They look at a yield curve, which is a graph showing the yields of bonds with different maturities. This curve helps show market expectations for future interest rates. By using this method, investors can find if a bond is priced incorrectly compared to the market.

Arbitrage also plays a huge role in international trade and currency values. Imagine a car is cheaper in the United States than in Canada. Canadians would buy the car in the U.S. to take advantage of the lower price. At the same time, Americans might buy cars in the U.S. to sell in Canada. These actions change the demand for the U.S. dollar and the Canadian dollar. Eventually, these shifts in demand cause the prices and the purchasing power of the currencies to balance out.

While arbitrage can seem safe, it carries significant risks in extreme situations. In rare cases, such as financial crises, these risks can lead to bankruptcy. This happens because arbitrageurs often use leverage, which is borrowed money, to increase their profits. If a large price move happens in the wrong direction, the losses can be massive. There are also counterparty risks, where the other person in a deal fails to pay. Finally, liquidity risk occurs when a trader lacks the cash needed to meet a margin requirement.