What Is “Beta” In Investing?

In the capital markets, balancing risk and reward is a primary task for active participants. On the risk side of the equation, beta is a tool used by traders and investors to quantify a security's exposure to systemic risk. Regardless of whether one is trading stocks, bonds, currency, futures or options, beta can be an invaluable asset when assessing risk and reward.

Beta Defined

According to the financial dictionary, beta (𝛣) is "the measure of an asset's risk in relation to the market or alternative benchmark."[1] Beta is not to be confused with alpha (𝛢), which is defined as being an inherent edge or advantage in the markets.

At its core, beta is the measurement of an asset's volatility and exposure to systemic risk. It may be thought of as a strictly numerical value or in graphical terms. Within the context of a graph, 𝛣 is a positively or negatively sloping line that represents the correlation of a security's performance with respect to the broader market. As a statistical value, the beta coefficient is a number that represents volatility and risk relative to an established benchmark. The statistical formula for 𝛣 may be expressed as follows:[2]

Assuming

  • Re = Security Return
  • Rm = Market Return

Beta Formula

  • Beta = (Covariance (Re, Rm) / Variance (Rm))

From a practical standpoint, 𝛣 can be a challenge to derive manually. The applications of covariance and variance are mathematically involved, which can make for an advanced computational process. Fortunately for active traders and investors, 𝛣 calculations are typically automated by spreadsheet programs such as Excel or specialised beta calculators.

Applications Of Beta (𝛣)

Beta may be applied in a variety of fashions to evaluate the risk of an individual security or portfolio. To illustrate basic functionality, assume that one is attempting to calculate 𝛣 for Alphabet Inc. (GOOG), a key constituent of the S&P 500. The S&P 500 is a broad-based index of the U.S. equities market and carries a beta coefficient of 1. Subsequently, the following GOOG beta values garner unique interpretations:

  • If GOOG has a beta of 1, then the stock is producing returns on par with the aggregate S&P 500 market.
  • If GOOG has a beta greater than 1, then the stock is producing returns at a multiple of the aggregate S&P 500 market.
  • If GOOG has a beta of zero, then the stock price moves little or not at all in relation to the S&P 500.
  • If GOOG has a beta less than 0, the stock is exhibiting an inverse correlation to the broader S&P 500.

As a general rule of thumb, the higher a security's beta value, the greater its profit potential, volatility and risk exposure. This concept is especially important when quantifying risk profiles for portfolios that combine holdings from multiple asset classes. From the perspective of specific asset/portfolio allocations, beta may be viewed in the following terms:

  • Beta = 1: Prominent large-cap stocks, diversified portfolios, and comprehensive index products (S&P 500).
  • Beta > 1: Growth-oriented stocks and portfolios, speculative and risk assets.
  • Beta = 0: Low volatility assets or portfolios such as select bonds and U.S. Treasuries.
  • Beta < 0: Assets or portfolios with negative betas are viewed as being hedging mechanisms. Gold and inverse ETFs are two examples.

Capital Asset Pricing Model (CAPM)

One of the most common uses of beta is to project how an investment may (or may not) perform over time. This is typically done within the context of the Capital Asset Pricing Model (CAPM). In simplest terms, the CAPM quantifies the relationship between the cost, assumed risk and expected return on an investment. The CAPM formula may be manipulated in a multitude of fashions to determine risk premiums or asset prices. It is calculated per the following:

Assumptions

  • Ra = Asset Price
  • Rf = Risk-Free Rate of Return
  • Beta = Asset Beta Value
  • Rm = Market Rate of Return

CAPM Formula

  • Ra = Rf + (Beta (Rm - Rf))

The CAPM formula may be altered to solve for asset price or rates of return. It's also often used in determining the cost of capital. However, whichever iteration is applied, beta remains an integral aspect of each calculation.

Important Considerations For Using Beta

Although beta is a staple of the financial industry, there are a few important items to remember when applying it in real world conditions. Below are several key elements of beta vital to its appropriate use:

Not Constant

When using beta to evaluate risk or project future performance, it's important to remember that values frequently change. Just because a security or portfolio has a certain beta today does not guarantee the same correlation tomorrow.

Unique Applications

Beta functions differently in each market where it is applied. For instance, 𝛣 is most commonly used to evaluate individual stock performance in comparison to the broader market. However, this type of interpretation is inherently difficult in forex, as currencies are traded against one another. Accordingly, forex beta is viewed in terms of periodic volatility which is commonly measured as standard deviation (σ).

Limited Predictive Value

While beta works well for identifying current volatility and systemic risk exposure, it does have limitations. Due to the fact that beta is based on historical pricing and performance data, it is less useful for projecting future market behaviour. In addition, pricing volatility can vary greatly over time in relation to shifting market dynamics.

Summary

Beta (𝛣) is a statistical device used to measure a security's volatility and performance relative to a benchmark. It is commonly used for evaluating stocks and as a part of the Capital Asset Pricing Model (CAPM). Although beta is a valuable tool for quantifying current risk and reward, it has limited predictive value.

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