Pairs Trade: Definition, How Strategy Works, and Example

What Is a Pairs Trade?

A pairs trade is a trading strategy that involves matching a long position with a short position in two stocks with a high correlation.

Understanding Pairs Trade

Pairs trading was first introduced in the mid-1980s by a group of technical analyst researchers that were employed by Morgan Stanley, the multinational investment bank and financial services company. The pairs trade strategy uses statistical and technical analysis to seek out potential market-neutral profits.

Market-neutral strategies are a key aspect of a pairs trade transaction. Market-neutral strategies involve long and short positions in two different securities with a positive correlation. The two offsetting positions form the basis for a hedging strategy that seeks to benefit from either a positive or negative trend.

A pairs trade strategy is based on the historical correlation of two securities. The securities in a pairs trade must have a high positive correlation, which is the primary driver behind the strategy’s profits. A pairs trade strategy is best deployed when a trader identifies a correlation discrepancy. Relying on the historical notion that the two securities will maintain a specified correlation, the pairs trade can be deployed when this correlation falters.

When pairs from the trade eventually deviate—as long as an investor is using a pairs trade strategy—they would seek to take a dollar matched the long position in the underperforming security and sell short the outperforming security. If the securities return to their historical correlation, a profit is made from the convergence of the prices.

Advantages and Disadvantages of Pairs Trade 

When a pairs trade performs as expected, the investor profits; the investor is also able to mitigate potential losses that would have occurred in the process. Profits are generated when the underperforming security regains value, and the outperforming security’s price deflates. The net profit is the total gained from the two positions.

There are several limitations for pairs trading. One is that the pairs trade relies on a high statistical correlation between two securities. Most pairs trades will require a correlation of 0.80, which can be challenging to identify. Second, while historical trends can be accurate, past prices are not always indicative of future trends. Requiring only a correlation of 0.80 can also decrease the likelihood of the expected outcome.

Example of Pairs Trade

To illustrate the potential profit of the pairs trade strategy, consider Stock A and Stock B, which have a high correlation of 0.95. The two stocks deviate from their historical trending correlation in the short-term, with a correlation of 0.50.

The arbitrage trader steps in to take a dollar matched the long position on underperforming Stock A and a short position on outperforming Stock B. The stocks converge and return to their 0.95 correlation over time. The trader profits from a long position and closed short position.