Recent from talks
Nothing was collected or created yet.
Alpha (finance)
View on WikipediaThis article needs additional citations for verification. (March 2016) |
Alpha is a measure of the active return on an investment, the performance of that investment compared with a suitable market index. An alpha of 1% means the investment's return on investment over a selected period of time was 1% better than the market during that same period; a negative alpha means the investment underperformed the market.
Alpha, along with beta, is one of two key coefficients in the capital asset pricing model used in modern portfolio theory and is closely related to other important quantities such as standard deviation, R-squared and the Sharpe ratio.[1]
In modern financial markets, where index funds are widely available for purchase, alpha is commonly used to judge the performance of mutual funds and similar investments. As these funds include various fees normally expressed in percent terms, the fund has to maintain an alpha greater than its fees in order to provide positive gains compared with an index fund. Historically, the vast majority of traditional funds have had negative alphas, which has led to a flight of capital to index funds and non-traditional hedge funds.
It is also possible to analyze a portfolio of investments and calculate a theoretical performance, most commonly using the capital asset pricing model (CAPM). Returns on that portfolio can be compared with the theoretical returns, in which case the measure is known as Jensen's alpha. This is useful for non-traditional or highly focused funds, where a single stock index might not be representative of the investment's holdings.
Definition in capital asset pricing model
[edit]The alpha coefficient () is a parameter in the single-index model (SIM). It is the intercept of the security characteristic line (SCL), that is, the coefficient of the constant in a market model regression.
where the following inputs are:
- : the realized return (on the portfolio),
- : the market return,
- : the risk-free rate of return, and
- : the beta of the portfolio.
- εi,t : the non-systematic or diversifiable, non-market or idiosyncratic risk
It can be shown that in an efficient market, the expected value of the alpha coefficient is zero. Therefore, the alpha coefficient indicates how an investment has performed after accounting for the risk it involved:
- : the investment has earned too little for its risk (or, was too risky for the return)
- : the investment has earned a return adequate for the risk taken
- : the investment has a return in excess of the reward for the assumed risk
For instance, although a return of 20% may appear good, the investment can still have a negative alpha if it's involved in an excessively risky position.
In this context, because returns are being compared with the theoretical return of CAPM and not to a market index, it would be more accurate to use the term of Jensen's alpha.
Origin of the concept
[edit]Efficient market hypothesis (EMH) states that share prices reflect all information, therefore stocks always trade at their fair value on exchanges. This would mean consistent alpha generation (i.e. better performance than the market) is impossible, and proponents of EMH posit that investors would benefit from investing in a low-cost, passive portfolio.[2]
A belief in EMH spawned the creation of market capitalization weighted index funds, which seek to replicate the performance of investing in an entire market in the weights that each of the equity securities comprises in the overall market.[3][4] The best examples for the US are the S&P 500 and the Wilshire 5000 which approximately represent the 500 most widely held equities and the largest 5000 securities respectively, accounting for approximately 80%+ and 99%+ of the total market capitalization of the US market as a whole.
In fact, to many investors,[citation needed] this phenomenon created a new standard of performance that must be matched: an investment manager should not only avoid losing money for the client and should make a certain amount of money, but in fact should make more money than the passive strategy of investing in everything equally (since this strategy appeared to be statistically more likely to be successful than the strategy of any one investment manager). The name for the additional return above the expected return of the beta adjusted return of the market is called "Alpha".
Relation to beta
[edit]Besides an investment manager simply making more money than a passive strategy, there is another issue: although the strategy of investing in every stock appeared to perform better than 75 percent of investment managers (see index fund), the price of the stock market as a whole fluctuates up and down, and could be on a downward decline for many years before returning to its previous price.
The passive strategy appeared to generate the market-beating return over periods of 10 years or more. This strategy may be risky for those who feel they might need to withdraw their money before a 10-year holding period, for example. Thus investment managers who employ a strategy that is less likely to lose money in a particular year are often chosen by those investors who feel that they might need to withdraw their money sooner.
Investors can use both alpha and beta to judge a manager's performance. If the manager has had a high alpha, but also a high beta, investors might not find that acceptable, because of the chance they might have to withdraw their money when the investment is doing poorly.
These concepts not only apply to investment managers, but to any kind of investment.
References
[edit]- ^ Banton, Caroline (2021-12-14). "5 Ways to Measure Mutual Fund Risk". Investopedia. Retrieved 2024-02-15.
- ^ Downey, Lucas. "Efficient Market Hypothesis (EMH): Definition and Critique". Archived from the original on 2024-05-13.
- ^ "How Does an Efficient Market Affect Investors?". Investopedia. 2023-09-15. Archived from the original on 2024-01-01.
- ^ Hayes, Adam (2024-03-05). "Capitalization-Weighted Index: Definition, Calculation, Example". Investopedia. Archived from the original on 2024-05-10.
Further reading
[edit]- Bruce J. Feibel. Investment Performance Measurement. New York: Wiley, 2003. ISBN 0-471-26849-6
External links
[edit]- International Association of CPAs, Attorneys, and Management (IACAM) (Free Business Valuation E-Book Guidebook)
- The financial-dictionary entry on alpha
- Investopedia Alpha Definition
- Five Technical Risk Ratios
- Alpha analysis for global equities Free alpha look-up
- Traders Magazine Seeking Alpha - New York hedge fund creates value trading index options
Alpha (finance)
View on GrokipediaCore Concepts
Definition
In finance, alpha is a measure of an investment's performance, representing the excess return achieved relative to a benchmark index, adjusted for the level of risk undertaken.[3] This metric isolates the portion of return attributable to active management or security selection rather than broad market movements.[4] A positive alpha indicates outperformance, suggesting that the investment has generated returns above those expected given its risk exposure, often reflecting managerial skill in forecasting or timing.[3] Conversely, a negative alpha signals underperformance, implying returns below the benchmark after risk adjustment.[4] Unlike total return, which captures the overall gain or loss from an investment including market effects, alpha specifically highlights the incremental value created by decisions that deviate from passive benchmark replication.[3] For example, if a portfolio returns 12% while its benchmark yields 10% under equivalent risk conditions, the alpha is 2%, demonstrating added value from active strategies.[3] This concept is frequently framed within the capital asset pricing model to ensure risk-adjusted comparability.[4]Mathematical Formulation
In the Capital Asset Pricing Model (CAPM), the expected return on an asset is formulated as , where is the risk-free rate, is the asset's beta measuring its systematic risk relative to the market, is the expected market return, and represents the market risk premium.[5] This equation derives from the model's equilibrium conditions, positioning assets along the Security Market Line (SML), which plots expected returns against beta in a linear relationship.[6] Alpha () emerges in the ex-post empirical test of CAPM through a time-series regression of the asset's excess returns on the market's excess returns: , where is the return on asset at time , is the market return at time , and is the error term with zero mean under CAPM.[7] Here, is the regression intercept, representing the average excess return not explained by the asset's beta exposure to market risk. If CAPM holds perfectly, ; a positive indicates the asset outperforms the SML on a risk-adjusted basis, plotting above the line, while signifies underperformance below the SML.[6] This formulation of alpha relies on key CAPM assumptions, including a single-period investment horizon, the absence of taxes and transaction costs, unlimited borrowing and lending at the risk-free rate, and market efficiency where the market portfolio is mean-variance efficient.[5] These conditions ensure that any deviation captured by alpha reflects true superior performance rather than market frictions or differing investor horizons.[6]Historical Background
Origin of the Concept
The concept of alpha in finance traces its roots to Harry Markowitz's modern portfolio theory, introduced in his 1952 paper "Portfolio Selection," which emphasized the evaluation of investments based on risk-adjusted returns rather than absolute returns alone.[8] Markowitz demonstrated that diversification could minimize unsystematic risk while optimizing portfolios along an efficient frontier, where expected returns are maximized for a given level of portfolio variance, thereby highlighting the need to distinguish between total risk and its components.[8] This foundation evolved with the development of the Capital Asset Pricing Model (CAPM) by William F. Sharpe in 1964, which provided a theoretical framework for pricing assets based on their contribution to overall market risk.[5] In CAPM, an asset's expected return is linearly related to its systematic risk, measured by beta, leaving any excess return attributable to factors beyond market exposure as a measure of non-systematic performance.[5] Sharpe's model thus introduced the idea of abnormal returns that could not be explained by systematic risk alone, representing the essence of what would later be quantified as alpha.[5] Sharpe's key contribution lay in conceptualizing this performance differential as the deviation between an asset's realized return and the return predicted by the CAPM equilibrium, enabling investors to assess whether a portfolio or security outperformed expectations adjusted for risk.[5] This was formally articulated in his seminal article "Capital Asset Prices: A Theory of Market Equilibrium under Conditions of Risk," published in The Journal of Finance, which built directly on Markowitz's diversification principles to derive market-wide equilibrium pricing.[5] The framework established alpha's role as a benchmark for evaluating managerial skill in generating returns independent of market movements. This foundational concept was later refined and explicitly termed "alpha" by Michael Jensen in his 1968 analysis of mutual fund performance, providing an empirical measure for the CAPM intercept.[7]Jensen's Alpha
In 1968, Michael C. Jensen published a seminal empirical study on mutual fund performance that introduced a key risk-adjusted measure of portfolio returns, now known as Jensen's alpha. This work built upon the foundational Capital Asset Pricing Model (CAPM) to assess whether fund managers could generate returns exceeding those expected from market exposure alone.[7] Jensen's methodology involved a regression-based approach to estimate the alpha for 115 open-end mutual funds over the 1945–1964 period.[7] He regressed each fund's monthly returns against the market returns to isolate the intercept term, representing the average excess return attributable to the manager's security selection skill after adjusting for systematic risk. This technique allowed for a direct test of managerial forecasting ability, distinguishing it from passive market strategies.[7] The empirical results revealed that the average alpha across the funds was negative, indicating underperformance relative to CAPM benchmarks even before accounting for fees.[7] Specifically, only 3 funds showed statistically significant positive alphas, with the vast majority failing to outperform a simple buy-and-hold market index on a risk-adjusted basis; after management expenses, no funds demonstrated superior skill.[7] These findings suggested that mutual fund managers lacked consistent predictive ability and could not justify their costs through excess returns. Jensen's alpha has since become the standardized term for this CAPM-derived performance metric, widely adopted in finance for evaluating active management and influencing subsequent research on market efficiency.[9] Its legacy lies in providing a rigorous, quantifiable framework that challenged claims of widespread managerial outperformance.[10]Relationships with Risk Measures
Relation to Beta
Beta serves as a measure of systematic risk, quantifying an asset's volatility relative to the overall market.[11] In the Capital Asset Pricing Model (CAPM), beta captures the portion of an asset's return variability attributable to market movements, where a beta greater than 1 indicates higher sensitivity to market fluctuations and thus greater systematic risk.[11] Alpha depends on beta by evaluating performance after isolating and accounting for the returns expected from beta-driven systematic risk.[12] Specifically, alpha represents the excess return generated beyond what the CAPM predicts based on the asset's beta, allowing investors to assess whether a manager has added value independent of market exposure.[13] In joint interpretation, alpha and beta together provide a fuller picture of risk-adjusted performance within the CAPM framework. A high beta paired with positive alpha suggests effective management of elevated systematic risk, as the asset delivers superior returns after adjusting for its market sensitivity. Conversely, a low beta combined with negative alpha indicates underperformance, where the asset fails to meet even modest market-related expectations.[11] For example, based on monthly data up to December 2011, Apple Inc. (AAPL) with a beta of 1.45 and alpha of 1.13% outperformed General Electric (GE) with a beta of 1.18 and alpha of 0.13% on a risk-adjusted basis, demonstrating how a higher alpha can signal stronger performance despite greater market risk exposure.[11]Comparison with Other Performance Metrics
Alpha, as a measure of excess return relative to systematic risk, differs from other risk-adjusted performance metrics in its focus on the Capital Asset Pricing Model (CAPM) framework.[14] The Sharpe ratio, introduced by William F. Sharpe, evaluates total excess return per unit of total risk, measured by the standard deviation of returns, making it suitable for assessing overall portfolio volatility including both systematic and unsystematic components.[15] In contrast, alpha isolates performance attributable to manager skill beyond what beta explains, ignoring unsystematic risk that the Sharpe ratio explicitly penalizes.[16] The Treynor ratio, developed by Jack Treynor, measures excess return per unit of systematic risk via beta, offering a ratio-based alternative to alpha's intercept from the CAPM regression.[14] While both alpha and the Treynor ratio emphasize systematic risk exposure in relation to the market, the Treynor metric normalizes returns by beta to gauge efficiency, whereas alpha quantifies absolute outperformance after beta adjustment.[15] This similarity positions the Treynor ratio as a complementary tool for CAPM adherents, but it assumes diversification eliminates unsystematic risk, much like alpha.[16] Investors adhering to CAPM principles often prefer alpha or the Treynor ratio to evaluate skill in generating returns above market expectations on a systematic risk basis.[14] Conversely, the Sharpe ratio is more appropriate for diversified portfolios where total risk matters, as it captures the full spectrum of volatility and rewards consistent excess returns regardless of market correlation.[15] A key limitation of alpha relative to these metrics is its disregard for unsystematic risk, which the Sharpe ratio addresses by incorporating standard deviation, potentially providing a more holistic view of performance in non-fully diversified contexts.[16] This oversight can lead to overestimation of manager ability if idiosyncratic volatility is high, whereas the Treynor ratio shares alpha's focus on beta but offers a proportional insight that may highlight relative efficiency more clearly.[14]Practical Applications
Portfolio Evaluation
In portfolio evaluation, alpha serves as a key metric for assessing the skill of active managers in mutual funds and hedge funds, where a positive alpha indicates the ability to generate excess returns beyond what would be expected from market exposure alone. For mutual funds, which typically track broad equity benchmarks, empirical studies have shown that few funds achieve sustained positive alpha, underscoring the challenges of consistent outperformance through security selection. In contrast, hedge funds often exhibit positive alphas when evaluated against multi-factor models, signaling potential managerial skill in exploiting non-linear strategies or alternative exposures, though this can be overstated if models fail to capture hidden betas.[1][17][18] Benchmarks for alpha calculation vary by asset class to ensure relevance; for equity-focused portfolios like mutual funds, the S&P 500 is a standard reference, capturing broad U.S. market performance, while alternative investments such as hedge funds employ customized benchmarks incorporating factors like trend-following or emerging market indices to better reflect their dynamic strategies.[17] To refine alpha estimates in portfolio evaluation, practitioners extend the single-factor Capital Asset Pricing Model (CAPM) to multi-factor frameworks, such as the Fama-French three-factor model, which adjusts for size (SMB) and value (HML) premiums alongside market risk, providing a more accurate measure of skill by isolating returns not explained by these common risk factors.[19] A prominent case study is Warren Buffett's Berkshire Hathaway, which has demonstrated sustained positive alpha relative to traditional benchmarks over decades, with an annualized alpha of approximately 12% from 1976 to 2011 when evaluated against public market factors, though much of this is attributable to systematic tilts toward value, quality, and low-volatility stocks amplified by moderate leverage.[20]Calculation Methods
To compute alpha for an asset or portfolio, the primary method involves collecting historical return data and applying linear regression analysis to isolate the intercept term, which represents alpha.[21] The process begins by gathering monthly returns for the asset or portfolio over a stable period, typically 3 to 5 years (36 to 60 months) to ensure sufficient data points for reliable estimation while capturing market cycles.[22] Next, obtain corresponding returns for a relevant benchmark index, such as the S&P 500 for U.S. equities, and the risk-free rate, often proxied by the yield on short-term U.S. Treasury bills.[23] Historical returns can be sourced from financial data providers like Yahoo Finance for adjusted closing prices to calculate percentage changes, or professional terminals like Bloomberg for comprehensive, real-time adjusted data including dividends and splits.[24] Risk-free rates are available from the U.S. Department of the Treasury website or integrated feeds in platforms like Bloomberg.[25] Once data is compiled, adjust returns to excess returns by subtracting the risk-free rate from both the asset/portfolio and benchmark series. Then, perform an ordinary least squares (OLS) linear regression of the asset's excess returns (dependent variable) against the benchmark's excess returns (independent variable); the resulting intercept coefficient is alpha, indicating average excess return not explained by market risk.[21] Several accessible tools facilitate this computation. In Microsoft Excel, import data into columns, use the Data Analysis ToolPak's Regression feature or the LINEST function to output the intercept as alpha, with options to annualize by multiplying by 12 for monthly data.[26] For more advanced analysis, Python's statsmodels library supports OLS regression via thesm.OLS function, allowing scripted automation with libraries like pandas for data handling from CSV exports of Yahoo Finance or Bloomberg.[27] Similarly, R's base lm function performs the regression efficiently, integrating well with packages like quantmod for direct data import from sources such as Yahoo Finance.
