Correlation is a statistical metric that measures the degree to which two securities move in relation to one another.
Understanding correlation
For Elephants constructing an investment portfolio, correlation is a mathematical tool used to assess risk and diversification. The metric is expressed as a correlation coefficient, which ranges from -1.0 to 1.0. A correlation of 1.0 indicates a perfect positive correlation, meaning the two assets always move in the exact same direction. A correlation of -1.0 indicates a perfect negative correlation, where the assets always move in opposite directions. A correlation of 0 means there is no linear relationship between the movements of the two assets.
Investors use correlation to manage overall portfolio volatility. When a portfolio contains assets that are highly correlated, the investments tend to rise and fall together. This creates higher risk during market downturns. By adding assets with a low or negative correlation to the existing holdings, investors offset potential losses. When one asset declines in value, an uncorrelated or negatively correlated asset may hold its value or increase.
Correlation is a dynamic measurement. The relationship between two securities changes over time due to shifting market conditions and broad economic cycles. Assets that typically show zero correlation can become highly correlated during periods of extreme financial stress. Investors recalculate correlation coefficients to ensure their diversification strategies remain effective.
It is a standard principle in statistics and finance that correlation does not imply causation. Two securities may have a high positive correlation without one directly influencing the other. They may both be reacting to an external variable, such as a shift in central bank interest rates or fluctuations in energy prices.
Example
Consider a portfolio containing stock in a company that cultivates premium marula fruit and stock in a company that organizes outdoor elephant tracking expeditions. When regional weather is highly favorable, the marula harvest is abundant and tourism surges. Both companies report higher earnings, and their stock prices rise together. These two stocks have a high positive correlation.
To diversify this portfolio, an investor might purchase shares in a company that manufactures indoor veterinary diagnostic equipment for wildlife sanctuaries. If a prolonged rainy season disrupts outdoor elephant expeditions, the tracking company’s stock price falls. The veterinary equipment company is unaffected by the weather and continues to sell its products to indoor clinics, maintaining steady revenue. The stock prices of the tracking company and the veterinary company do not move together, demonstrating a low correlation. Adding the veterinary stock reduces the overall risk of the portfolio.