Investors, researchers, and analysts rely on several models and theories to analyze and measure risk in the financial markets. Two of the most popular models used for asset pricing and risk assessment are the Capital Asset Pricing Model (CAPM) and the Arbitrage Pricing Theory (APT). Although both models are widely used in finance, they have several fundamental differences. This essay aims to provide a comprehensive overview of the differences between CAPM and APT and their application in finance.
Introduction to CAPM and APT
The Capital Asset Pricing Model (CAPM) is a financial model that explains the relationship between systematic risk and expected returns on an asset. The model uses beta (β) to measure systematic risk, which is the measure of an asset’s volatility compared to the overall market. CAPM suggests that the expected return on an asset is proportional to the market risk premium (MRP), which is the difference between the expected market return and the riskfree rate of return.
The Arbitrage Pricing Theory (APT), on the other hand, is a financial model that uses multiple factors to determine the expected return on an asset. Unlike CAPM, which only considers one factor (systematic risk), APT assumes that an asset’s return is influenced by multiple factors, including macroeconomic variables, market trends, and other relevant factors.
Read Also: Impact of Financing Structure on NPV Calculations
Differences between CAPM and APT
The following are some of the key differences between CAPM and APT.

Assumptions
CAPM assumes that there is only one factor that influences the expected return on an asset (systematic risk), while APT assumes that multiple factors impact an asset’s expected return.
Assumptions play a critical role in distinguishing between CAPM and APT. CAPM is based on the assumption that there is only one factor that influences the expected return on an asset, which is the systematic risk represented by the market portfolio. On the other hand, APT assumes that multiple factors impact an asset’s expected return, and the relationship between the factors and the asset’s return can be expressed through a linear equation. In this way, APT is more flexible than CAPM, which only accounts for one source of risk. This assumption is one of the main reasons for the development of APT as an alternative to CAPM.
The Capital Asset Pricing Model (CAPM) and the Arbitrage Pricing Theory (APT) are two widely used financial models used to estimate the expected return on an investment. While both models serve the same purpose, they differ significantly in their underlying assumptions and methods. In this essay, we will explore the key differences between CAPM and APT, with a focus on their assumptions.
CAPM Assumptions:
CAPM is a widely used model that calculates the expected return on an asset based on the asset’s beta, the expected market return, and the riskfree rate. The model is based on several assumptions, including:
 Investors are rational and riskaverse.
 The market is efficient, and all investors have access to the same information.
 There is only one factor that influences the expected return on an asset, which is the systematic risk represented by the market portfolio.
 The asset’s idiosyncratic risk can be diversified away by holding a welldiversified portfolio of assets.
APT Assumptions:
The Arbitrage Pricing Theory (APT) is an alternative to CAPM that accounts for multiple sources of risk in estimating expected returns. The APT model assumes that the expected return on an asset is a linear function of several macroeconomic and other relevant factors that influence an asset’s return. Some of the key assumptions of APT include:
 Investors are rational and riskaverse.
 There are multiple factors that impact an asset’s expected return, including macroeconomic variables, market trends, and other relevant factors.
 The relationship between the factors and the asset’s return can be expressed through a linear equation.
 The asset’s idiosyncratic risk can be diversified away by holding a welldiversified portfolio of assets.
Differences Between CAPM and APT:
The key difference between CAPM and APT is the number of factors they consider in estimating an asset’s expected return. CAPM assumes that there is only one factor (beta) that influences an asset’s expected return, while APT considers multiple factors. In addition, CAPM is based on the assumption that all investors have access to the same information, while APT assumes that investors may have different information and may interpret it differently. Finally, APT is considered to be more flexible than CAPM, as it allows for the inclusion of additional factors that may impact an asset’s expected return.
Both CAPM and APT are widely used models for estimating expected returns on investments. However, they differ significantly in their underlying assumptions and methods. CAPM assumes that there is only one factor that influences an asset’s expected return, while APT considers multiple factors. Investors and financial analysts should be aware of the assumptions underlying each model when choosing which model to use in their analysis.

Factors
CAPM only considers one factor, beta (β), while APT considers multiple factors, including macroeconomic variables, market trends, and other relevant factors.
The main difference between CAPM and APT lies in the number of factors they consider in determining an asset’s expected return. CAPM is based on the assumption that there is only one factor that influences an asset’s expected return, which is the systematic risk represented by the market portfolio. In other words, CAPM assumes that an asset’s return is solely influenced by the overall market movement.
On the other hand, APT assumes that multiple factors impact an asset’s expected return. These factors can include macroeconomic variables, market trends, and other relevant factors that may influence the asset’s return. The relationship between these factors and an asset’s return can be expressed through a linear equation, allowing for a more comprehensive analysis of an asset’s expected performance.
While CAPM only accounts for one source of risk (systematic risk), APT considers multiple sources of risk that may impact an asset’s expected return. This assumption is one of the primary reasons for the development of APT as an alternative to CAPM, as it allows for a more flexible and comprehensive approach to asset pricing.

Risk
CAPM only measures systematic risk, while APT measures both systematic and unsystematic risk.
CAPM vs APT: Differences in Measuring Risk
Capital Asset Pricing Model (CAPM) and Arbitrage Pricing Theory (APT) are two popular models used in finance to determine the expected return on an asset. One of the primary differences between these two models is how they measure risk.
CAPM: Measures Systematic Risk Only
CAPM is based on the assumption that an asset’s expected return is determined by the asset’s systematic risk, which is the risk that cannot be diversified away through portfolio diversification. CAPM measures systematic risk through beta (β), which represents an asset’s sensitivity to movements in the overall market. Therefore, CAPM only considers systematic risk when measuring risk.
APT: Considers Both Systematic and Unsystematic Risk
In contrast, APT considers both systematic and unsystematic risk when measuring risk. Systematic risk is still included in APT, but it also considers other factors that affect an asset’s return, such as macroeconomic variables, market trends, and other relevant factors. This makes APT more comprehensive in measuring risk than CAPM.
Diversification of Unsystematic Risk
One advantage of APT over CAPM is that it provides a way to diversify unsystematic risk. Unsystematic risk is the risk that can be reduced through portfolio diversification, and APT takes into account various factors to determine how to diversify the portfolio to reduce this risk.
The primary difference between CAPM and APT in measuring risk is that CAPM only considers systematic risk, while APT considers both systematic and unsystematic risk. While both models have their advantages and disadvantages, APT’s consideration of multiple factors makes it a more comprehensive model in measuring risk.

Accuracy
CAPM is considered a less accurate model than APT because it only uses one factor to measure expected returns, while APT considers multiple factors.
Accuracy is another area where CAPM and APT differ. CAPM is considered a less accurate model than APT because it only uses one factor to measure expected returns – beta (β), which may not capture all the relevant factors that impact an asset’s return. On the other hand, APT is considered more accurate because it considers multiple factors that affect an asset’s expected return, making it a more comprehensive model. With APT, a larger number of factors can be considered, which may result in more accurate predictions of asset returns.
Accuracy is a crucial aspect of any financial model used to measure expected returns. CAPM and APT are two popular models that differ in their approach to measuring accuracy.
CAPM uses only one factor to measure expected returns, which is beta (β). Beta is a measure of an asset’s sensitivity to movements in the overall market. However, this measure may not capture all the relevant factors that impact an asset’s return, making CAPM less accurate than APT.
In contrast, APT considers multiple factors that affect an asset’s expected return, such as macroeconomic variables, market trends, and other relevant factors. APT’s consideration of multiple factors makes it a more comprehensive model than CAPM, as a larger number of factors can be considered in the analysis.
APT’s potential for more accurate predictions is one of its key advantages over CAPM. By considering multiple factors, APT may result in more accurate predictions of asset returns, providing investors with a more reliable estimate of future performance.
While both CAPM and APT are popular models used to measure expected returns, they differ in their approach to accuracy. CAPM’s use of only one factor may result in less accurate predictions of asset returns, while APT’s consideration of multiple factors may provide a more comprehensive and accurate analysis.

Simplicity
CAPM is a relatively simple model that is easy to use and understand, while APT is more complex and requires extensive data and analysis.
CAPM is a simple and straightforward model that only requires the estimation of the market risk premium and the beta of an asset. This simplicity makes it a popular model for investors, especially those who are not wellversed in finance or economics. However, its simplicity is also a disadvantage, as it may not capture all the relevant factors that affect an asset’s return.
APT, on the other hand, is a more complex model that considers multiple factors that may impact an asset’s expected return. This makes APT a more comprehensive model than CAPM, but also more difficult to use and understand. APT requires the identification of relevant factors and the estimation of their impact on an asset’s return, which may require extensive data and analysis.
Overall, CAPM is a simpler and more accessible model for investors, while APT is more comprehensive but also more complex. Choosing which model to use may depend on the investor’s level of expertise, the availability of data, and the specific characteristics of the asset being analyzed.

Market efficiency
CAPM assumes that markets are efficient and that all investors have the same information, while APT assumes that markets are not always efficient, and some investors have access to more information than others.
CAPM assumes that markets are efficient, which means that all investors have the same information about an asset, and the market price reflects its true value. In other words, the market price of an asset is assumed to be the best estimate of its true value. On the other hand, APT does not assume that markets are always efficient. Instead, APT recognizes that some investors may have access to more information than others, leading to differences in their expectations of an asset’s future return. As a result, APT allows for market inefficiencies and provides a framework for identifying mispriced assets.

Application
CAPM is widely used in finance, particularly in portfolio management and asset pricing, while APT is mainly used by financial analysts and researchers.
CAPM has widespread application in finance, particularly in portfolio management and asset pricing. The model’s simplicity and ease of use have made it a popular tool for investors and analysts. CAPM is often used to determine the expected return of an asset based on its level of risk, which can help investors make informed investment decisions.
APT, on the other hand, is mainly used by financial analysts and researchers. The model’s complexity and the need for extensive data and analysis make it less accessible to most investors. APT is often used in academic research to identify and measure the impact of multiple factors on an asset’s return, helping researchers to gain a deeper understanding of the underlying dynamics of financial markets.

Predictability
CAPM is less reliable in predicting asset prices than APT because it only uses one factor to predict returns, while APT uses multiple factors.
APT is considered to be more reliable than CAPM in predicting asset prices. This is because APT considers multiple factors that can affect an asset’s return, making it a more comprehensive model for predicting returns. In contrast, CAPM relies solely on beta (β) as a measure of risk and only considers one factor to predict returns, which can limit its ability to accurately predict future asset prices. As a result, APT is often preferred over CAPM for forecasting returns and pricing assets.

Riskfree rate
CAPM assumes a constant riskfree rate, while APT assumes that the riskfree rate can change over time.
CAPM assumes a constant riskfree rate, which is usually the rate of return on a government bond with no default risk. This assumption is based on the idea that investors can borrow and lend at this riskfree rate to build their portfolios.
On the other hand, APT assumes that the riskfree rate can change over time, reflecting changes in the economy or in the creditworthiness of the issuer. This means that APT is more flexible than CAPM in accounting for changes in the riskfree rate, which can affect an asset’s expected return.

Limitations
Both models have limitations, but CAPM’s main limitation is its inability to account for unsystematic risk, while APT’s main limitation is its complexity and the difficulty in identifying the relevant factors.
Summary: Differences between CAPM and APT
CAPM
 Singlefactor model: CAPM only considers one factor, beta (β), when estimating expected returns.
 Systematic risk: CAPM only measures systematic risk, which cannot be diversified away through portfolio diversification.
 Accuracy: CAPM is considered a less accurate model than APT due to its reliance on a single factor to predict returns.
 Simplicity: CAPM is a relatively simple model that is easy to use and understand, compared to APT.
 Market efficiency: CAPM assumes that markets are efficient and that all investors have the same information.
 Riskfree rate: CAPM assumes a constant riskfree rate.
APT
 Multifactor model: APT considers multiple factors, including macroeconomic variables, market trends, and other relevant factors, when estimating expected returns.
 Both systematic and unsystematic risk: APT measures both systematic and unsystematic risk, which can be diversified away through portfolio diversification.
 Accuracy: APT is considered more accurate than CAPM due to its consideration of multiple factors when predicting returns.
 Complexity: APT is more complex and requires more data and analysis than CAPM.
 Application: APT is mainly used by financial analysts and researchers.
 Market efficiency: APT assumes that markets are not always efficient, and some investors have access to more information than others.
 Riskfree rate: APT assumes that the riskfree rate can change over time.
 Limitations: APT’s main limitation is its complexity and the difficulty in identifying the relevant factors.
Conclusion
The differences between CAPM and APT are significant and can affect the accuracy of asset pricing and risk assessment. Although both models have their strengths and weaknesses, the choice of which model to use depends on the specific needs and goals of the investor or analyst. CAPM is simple and widely used, making it ideal for portfolio management and asset pricing. APT, on the other hand, is more complex but offers more accuracy in predicting asset prices and risk. Ultimately, the decision on which model to use should be based on the investor’s specific needs.