# What is CAPM (Capital Asset Pricing Model): Detailed Explanation

Created on 27 Feb 2023

Wraps up in 14 Min

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Updated on 24 May 2024

Imagine that you are about to take a cross-country road trip. You've got your car, your maps, your music playlist, and your snacks all ready to go. But before you hit the road, you realise that you need to figure out the best route to take to reach your final destination. You start to think about the various factors that could impact your journey - traffic patterns, weather conditions, road closures, and so on.

In the world of finance, investors face a similar challenge when trying to navigate the stock market. They need to figure out the best way to get from point A (their current portfolio) to point B (their desired investment outcomes). And just like a road trip, there are many factors that can impact their journey - market conditions, economic trends, company performance, and so on.

This is where the Capital Asset Pricing Model (CAPM) comes in. It is a powerful tool that helps investors to understand the relationship between risk and reward in the stock market. By using it, investors can calculate investment risk and expected return. So, let's buckle up and take a closer look at this important concept of CAPM.

## What is CAPM?

Let's say you're considering two different investment opportunities: buying shares of a well-established company with a long history of consistent returns or investing in a brand-new startup with no proven track record. Generally, an established company is considered less risky, while a startup is more risky.

According to the CAPM model, you should expect a higher return on the startup investment to compensate for the increased risk. Conversely, you should expect a lower return on the established company investment since it's considered safer.

Simply put, CAPM is a theory that helps investors determine how much return they can expect to earn on a particular investment based on the level of risk involved. It suggests that the expected return on investment should be higher if it's considered riskier and lower if it's considered safer.

For example, investing in stocks is generally considered riskier than investing in bonds, so stocks are expected to have a higher return than bonds.

Now, when we talk about risk, there are two types that we need to consider - systematic and unsystematic risks.

Systematic risk refers to the overall risk inherent in the entire market or economy, which cannot be diversified away. This risk affects all investments and is beyond the control of individual investors. Factors such as inflation, interest rates, and political events can all contribute to systematic risk.

On the other hand, unsystematic risk is specific to an individual company or industry and can be diversified away by investing in a diverse portfolio. It can be caused by factors such as management decisions, labour strikes, or product recalls.

It is useful to understand the difference between systematic and unsystematic risk is crucial for investors. It helps them determine how much risk they're willing to take on and how to allocate their portfolio accordingly. By diversifying their portfolio and investing in a mix of assets with varying levels of systematic and unsystematic risks, investors can minimise their overall risk and maximise their potential returns.

## CAPM: The History of a Revolutionary Concept in Finance

CAPM has become one of the most widely used financial models for investment analysis and portfolio management. It was developed in the 1960s by a brilliant economist named William Sharpe.

The need for such a model arose because investors were looking for a better way to determine the expected return on an investment, given the level of risk involved. Before the advent of CAPM, investors used to rely on trial and error or simply follow the advice of a financial advisor to make investment decisions.

Sharpe's idea was to create a model that would explain the relationship between risk and return in a simple and systematic way. He argued that an investment's expected return should not depend only on its riskiness but also on the riskiness of the overall market.

In other words, the expected return on investment should be proportional to its beta, a measure of its systematic risk. This led to the development of the CAPM formula, which we now use to calculate the expected return of an investment based on its beta and the risk-free rate of return.

Over the years, many other economists have contributed to the development of the CAPM model, refining it and adding new insights. Today, it is an essential tool for investors looking to make informed investment decisions based on a systematic and scientific approach.

## CAPM Made Simple: Key Terminology

Are you ready to enter the world of finance and asset pricing? Well, before we get to the nitty-gritty of the CAPM, let's get familiar with some of the key terminologies that form the backbone of this concept.

**1. Risk-free Rate:** This refers to the theoretical rate of return of an investment that carries no risk, typically represented by government bonds. It is the minimum return an investor should expect from any investment that carries no risk of losing money.

**2. Market Risk Premium:** This is the excess return an investor expects to receive from investing in a risky asset over and above the risk-free rate of return. It represents the additional compensation required by an investor for taking on market risk.

**3. Beta:** Beta is a measure of the volatility or systematic risk of an asset relative to the overall market. It measures how an asset's price is likely to move relative to changes in the overall market. A beta of 1 indicates that an asset moves in line with the market, while a beta of less than 1 indicates that it is less volatile than the market, and a beta of greater than 1 indicates that it is more volatile than the market.

**4. Expected Return:** The expected return is the return an investor expects to receive from an investment over a particular period. It is calculated by multiplying the investor's required rate of return by the asset's beta.

**5. Required Rate of Return:** The required rate of return is the minimum return an investor expects to receive for investing in a particular asset. It is calculated by adding the risk-free rate of return to the market risk premium, and then multiplying this sum by the asset's beta.

## CAPM Formula Explained: A Practical Approach

Are you curious to know how investors determine the expected return for investing in a security? Well, it's all thanks to the Capital Asset Pricing Model (CAPM) formula! The CAPM formula helps investors calculate the expected return of a security by factoring in the risk-free return and a risk premium.

Now, what is a risk premium, you might ask? It's simply the rate of return that's higher than the risk-free rate. It's the compensation that an investor receives for taking on systemic risk that can't be diversified away. In other words, it's the extra reward an investor expects to receive for taking on additional risk.

So, the formula for the expected return (ER) on a security is:

Expected return (ER) = Risk-free rate (RFR) + Beta (β) x (Market return (MR) - Risk-free rate (RFR))

The CAPM formula has three important components that investors should know.

- Expected return (ER) is the return that an investor expects to receive on a particular asset.
- The risk-free rate (RFR) is the return that an investor can earn on a safe and secure investment, such as a government bond.
- The market return (MR) is the return that investors can expect to earn on a comparable market index, such as the Nifty 50 or Sensex.

The difference between the market return and the risk-free rate is known as the risk premium, which is also referred to as the market risk premium.

While estimating market returns can vary according to asset class, investors can use historical data from popular indices such as the Nifty 50 or Sensex to calculate the market return. By understanding these key terms, investors can use the CAPM formula to determine the expected return of an asset.

## Example of CAPM

To calculate the expected return, you first need to determine the risk-free rate of return, which is the return on an investment with zero risk. This is usually determined by the yield on government bonds, which are considered to be virtually risk-free in India. Let's say the current yield on a 10-year government bond is 6%.

Next, you need to determine the expected return of the market, which can be estimated using a market index like the BSE Sensex or the Nifty 50. Let's say the expected return of the market is 12%.

The next step is to calculate the beta of the stock in question. Beta measures the volatility of a stock compared to the market. Let's say the beta of the stock is 1.5.

Now that you have all the inputs, you can use the CAPM formula to calculate the expected return of the stock:

Expected return (ER) = Risk-free rate (RFR) + Beta (β) x (Market return (MR) - Risk-free rate (RFR))

Expected return = 6% + 1.5 x (12% - 6%)

Expected return = 15%

The calculated expected return of 15% is the return an investor should expect from the stock based on its risk level.

The CAPM formula can also be used to determine whether a stock is undervalued or overvalued. If the actual return of the stock is lower than 15%, it could be considered undervalued and a good investment opportunity. If the actual return is higher than 15%, the stock may be overvalued and not a good investment opportunity.

## Role of Beta in CAPM

Let's talk about beta - the superhero of the stock market world! Beta is a measure of the volatility of a stock in relation to the overall market. It helps investors understand how much a stock's price may move in response to the ups and downs of the market.

Now, imagine a stock that moves in perfect harmony with the market. Its beta would be one. But if a stock has a beta of 1.3, it means that for every 10% increase in the market, the stock's price may go up by 13%! That's like a superhero power that investors can use to their advantage.

On the other hand, a stock with a negative beta (like -0.8) means that it moves in the opposite direction of the market. So if the market goes up by 10%, the stock may only go up by 8%. That's like a counter-force that investors need to be aware of.

When combined with the risk premium of an investment, beta helps investors calculate the potential return they can expect for taking on that additional risk. So, understanding beta is crucial for any investor who wants to make informed decisions in the stock market.

In short, beta is like a sidekick to investors, helping them navigate the twists and turns of the stock market.

## How to calculate Beta

Want to be a Beta Master? Here's How to Calculate Beta for Any Security Like a Pro! Follow These Step-by-Step Instructions and Unlock the Secrets of Market Risk.

**1. Choose a benchmark index:** Start by selecting a benchmark index that closely represents the market in which the security trades, BSE Sensex or the NSE Nifty.

**2. Determine the historical returns of the security and the benchmark:** Collect historical data of the security and benchmark index returns for a specific period, usually 2-5 years. For example, if you want to calculate the beta of a stock for the past year, you need to collect data of the stock prices and benchmark index prices for the past year.

**3. Calculate the average returns of the security and the benchmark:** Add up all the returns of the security and benchmark index over the period and divide by the number of years to calculate the average returns.

**4. Calculate the covariance of the security and benchmark:** Covariance measures how the returns of the security move in relation to the benchmark index. You can use a financial calculator or a spreadsheet to calculate the covariance.

**5. Calculate the variance of the benchmark:** Variance measures the volatility of the benchmark index returns over the same period.

**6. Calculate the beta of the security:** Divide the covariance of the security and benchmark by the variance of the benchmark.

For example, let's say you want to calculate the beta of a security, with the NSE Nifty as the benchmark index. You have collected the stock prices and Nifty prices for the past year, and their returns are as follows:

Stock returns: 20%, 15%, -5%, 10%, 12%

Nifty returns: 18%, 16%, -3%, 11%, 14%

1. Choose a benchmark index: NSE Nifty

2. Determine the historical returns of the security and the benchmark:

Stock average return = (20% + 15% - 5% + 10% + 12%) / 5 = 10.4%

Nifty average return = (18% + 16% - 3% + 11% + 14%) / 5 = 11.2%

3. Calculate the covariance of the security and benchmark: Covariance = Σ [(Rstock - Rstock avg) * (Rnifty - Rnifty avg)] / (n-1)

Covariance = [(20%-10.4%)(18%-11.2%) + (15%-10.4%)(16%-11.2%) + (-5%-10.4%)(-3%-11.2%) + (10%-10.4%)(11%-11.2%) + (12%-10.4%)*(14%-11.2%)] / (5-1)

Covariance = 105.12%

4. Calculate the variance of the benchmark: Variance = Σ [(Rnifty - Rnifty avg)^2] / (n-1)

Variance = [(18%-11.2%)^2 + (16%-11.2%)^2 + (-3%-11.2%)^2 + (11%-11.2%)^2 + (14%-11.2%)^2] / (5-1)

Variance = 6.8%

Step 5: Calculate the beta of the security: Beta = Covariance / Variance

Beta = 105.12% / 6.8% = 15.44

Therefore, the beta of the stock is 15.44, indicating that the stock is more volatile than the market.

CAPM: A Double-Edged Sword - Advantages and Disadvantages

Advantages and disadvantages of the Capital Asset Pricing Model (CAPM) are important to consider when making investment decisions. Let's explore some of the advantages and disadvantages of using CAPM.

## Advantages of using CAPM in investment analysis:

**1. Provides a benchmark:** CAPM provides a standard against which the performance of a portfolio or individual security can be measured.

**2. Incorporates market risk:** CAPM accounts for market risk, which is a crucial factor in investment decisions. By considering market risk, investors can make informed decisions about potential investments.

**3. Helps in determining required rate of return:** CAPM helps investors determine the required rate of return for a given investment based on its risk profile. This can aid in portfolio management by helping investors optimise their portfolio for risk and return.

## Practical applications of CAPM in portfolio management and risk assessment:

**1. Asset allocation:** CAPM can be used to allocate assets in a portfolio based on the expected return and risk of each asset. This can help investors optimise their portfolio for risk and return.

**2. Performance evaluation:** CAPM can be used to evaluate the performance of a portfolio or individual security by comparing its actual return to its expected return based on the model.

**3. Risk assessment:** CAPM can be used to assess the risk of an investment based on its beta value. By understanding the level of risk associated with an investment, investors can make informed decisions about potential investments.

## Drawbacks of relying solely on CAPM

**1. Assumptions may not hold:** CAPM relies on certain assumptions, such as the efficient market hypothesis, which may not always hold true in real-world scenarios. Therefore, the model may not be an accurate representation of the market and may lead to poor investment decisions.

**2. Limited in scope:** CAPM only takes into account market risk and assumes that all investors have access to the same information. This means that it may not fully capture other factors that can impact the value of an investment.

**3. Relies on historical data:** CAPM relies on historical data to estimate market risk and return, which may not always be a reliable predictor of future performance.

## Assumptions of CAPM

CAPM is a widely used financial model that helps investors evaluate the expected returns of a particular asset. However, like all models, the CAPM is based on certain assumptions that need to hold true for the model to be valid. Here are some of the key assumptions of CAPM:

**1. Investors are rational:** CAPM assumes that investors are rational and always seek to maximise their returns while minimising their risks. Investors are assumed to be risk-averse, meaning that they require compensation for taking on additional risk.

**2. All investors have access to the same information:** The CAPM assumes that all investors have access to the same information about the asset being evaluated. This means that investors will arrive at the same conclusion about the expected returns and risk associated with the asset.

**3. No transaction costs:** CAPM assumes that there are no transaction costs associated with buying or selling assets. This means that investors can trade freely without incurring any additional costs.

**3. Investors can lend or borrow at the risk-free rate:** The CAPM assumes that investors can borrow and lend money at the risk-free rate of return, which is the return on a risk-free asset such as a government bond.

**4. The market is efficient:** CAPM assumes that the market is efficient, meaning that all available information is reflected in the price of an asset. This means that it is impossible for investors to consistently outperform the market by using their own knowledge or analysis.

While these assumptions may simplify the model and make it easier to use, they may not always hold true in the real world. It is important for investors to be aware of these assumptions and evaluate their investment decisions accordingly.

## Problems with CAPM

CAPM sees major use in finance to calculate the expected return on an investment. However, there are certain problems associated with CAPM that investors and financial analysts should be aware of. Here are some of the main problems with CAPM:

**1. Unrealistic assumptions:** CAPM is based on a number of assumptions that may not hold true in the real world. For example, it assumes that investors have access to perfect information and that all investors have the same expectations about future returns. This is not always the case in practice.

**2. Reliance on historical data:** CAPM relies heavily on historical data to estimate the expected return and risk of an investment. However, past performance does not always predict future results. This can lead to inaccurate estimates of expected return and risk.

**3. Inability to account for market anomalies:** CAPM assumes that all assets are priced efficiently and that there are no market anomalies that could cause a particular stock or asset to deviate from its expected return. However, there are instances where certain assets may be over or undervalued due to market inefficiencies.

**4. Failure to consider unsystematic risk:** CAPM only accounts for systematic risk, which is risk that is inherent to the entire market. It does not account for non-systematic risk, which is risk that is specific to a particular company or industry. This means that CAPM may not be an accurate measure of risk for individual stocks or assets.

**5. Beta may not accurately reflect risk:** CAPM uses beta as a measure of risk, which is the covariance between an asset's returns and the returns of the market. However, beta may not accurately reflect the risk of an asset, as it only takes into account the relationship between an asset and the market, and not other factors that could affect its returns.

Overall, while CAPM is a useful tool for estimating expected return and risk, it is important to be aware of its limitations and potential problems when using it to make investment decisions.

#### The Bottom Line

While CAPM is a valuable financial model that has transformed the way we think about risk and return, it's essential to understand both its advantages and limitations. The simplicity and accuracy of the model make it an appealing choice for investors, but it's crucial to recognize that no model is perfect. CAPM's limitations, including the reliance on historical data, the assumption of a single risk factor, and the failure to account for non-systematic risks, should be considered when using the model.

Investors must use CAPM in conjunction with other tools and analyses, such as fundamental analysis and technical analysis, to make informed investment decisions. By understanding the limitations and potential drawbacks of CAPM, investors can use it more effectively and avoid costly mistakes. Ultimately, CAPM is just one tool in the investor's toolkit, and it's up to us to use it wisely and with caution.