What is Portfolio Optimization?

Explanation

An optimal portfolio is said to have the highest Sharpe ratioSharpe RatioSharpe Ratio, also known as Sharpe Measure, is a financial metric used to describe the investors’ excess return for the additional volatility experienced to hold a risky asset. You can calculate it by, Sharpe Ratio = {(Average Investment Rate of Return – Risk-Free Rate)/Standard Deviation of Investment Return} read more, which measures the excess return generated for every unit of risk taken.

Portfolio optimization is based on Modern Portfolio Theory (MPTMPTAn investment model like modern portfolio theory or MPT allows investors to choose from a variety of investment options comprising of a single portfolio for earning maximum benefits and that too at a market risk which is way lower than the various underlying investments or assets.read more). The MPT is based on the principle that investors want the highest return for the lowest risk. To achieve this, assets in a portfolio should be selected after considering how they perform relative to each other, i.e., they should have a low correlationCorrelationCorrelation is a statistical measure between two variables that is defined as a change in one variable corresponding to a change in the other. It is calculated as (x(i)-mean(x))*(y(i)-mean(y)) / ((x(i)-mean(x))2 * (y(i)-mean(y))2.read more. Any optimal portfolio based on the MPT is well-diversified to avoid a crash when a particular asset or asset class underperforms.

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Process of Optimal Portfolio

Asset AllocationAsset AllocationAsset Allocation is the process of investing your money in various asset classes such as debt, equity, mutual funds, and real estate, depending on your return expectations and risk tolerance. This makes it easier to achieve your long-term financial goals.read more for an optimal portfolio is essentially a two-part process:

  • Selecting Asset Classes – Portfolio managersPortfolio ManagersA portfolio manager is a financial market expert who strategically designs investment portfolios.read more first choose the asset classes they want to allocate funds to, then decide the weight of every asset class included. Common asset classesAsset ClassesAssets are classified into various classes based on their type, purpose, or the basis of return or markets. Fixed assets, equity (equity investments, equity-linked savings schemes), real estate, commodities (gold, silver, bronze), cash and cash equivalents, derivatives (equity, bonds, debt), and alternative investments such as hedge funds and bitcoins are examples.read more include Equities, Bonds, Gold, and Real Estate.Selecting Assets within Class – After deciding the asset classes, the manager decides how much of a particular stock or a bond she wants to include in the portfolio. The Efficient Frontier represents the risk-return relationship of an efficient portfolio on a graph. Each point on this curve represents an efficient portfolio.

Examples of Portfolio Optimization

Let’s see some practical examples of portfolio optimization to understand it better.

Example #1

If we take an example of Apple and Microsoft based on their monthly returns for the year 2018, the following graph shows the Efficient Frontier for a portfolio consisting only of these two stocks:

The X-axis is the standard deviation, and the y-axis is the portfolio return for the level of risk. If we combine this portfolio with a risk-free asset, the point on this graph where the Sharpe ratio is maximized represents the optimal portfolio. It is the point at which the capital allocation lineCapital Allocation LineThe capital allocation line, which also refers to the capital market line, is a graph used to measure the risk related to securities and defines the relationship (the combination of) between risky and risk-free assets, and the line on the graph represents it. It is also known as a reward to variability ratio.read more is tangential to the efficient frontier. The reason behind this is that at that point, the Sharpe ratio (which measures the increase in expected returnExpected ReturnThe Expected Return formula is determined by applying all the Investments portfolio weights with their respective returns and doing the total of results. Expected return = (p1 * r1) + (p2 * r2) + ………… + (pn * rn), where, pi = Probability of each return and ri = Rate of return with probability. read more for every additional unit of risk taken) is the highest.

Example #2

Suppose we want to combine a risky portfolio having only BestBuy and AT&T stocks and a risk-free asset with a return of 1%. We will plot the Efficient Frontier based on the return data for these stocks and then take a line that starts at 1.5 on the Y-axis and is tangential to this Efficient Frontier.

The X-axis represents the Standard Deviation, and Y-axis represents the return of the portfolio Of The PortfolioThe portfolio return formula calculates the return of the total portfolio consisting of the different individual assets. The formula is computed by calculating the return on investment on individual asset multiplied with respective weight class in the total portfolio and adding all the resultants together. Rp = ∑ni=1 wi riread more. An investor who wishes to take on less risk can move to the left of this point, and high risk-taking investors can move to the right. An investor who does not wish to take any risk at all would invest all the money in the risk-free asset but, simultaneously, limit their portfolio return to 1%. An extra return will be earned by taking the risk.

Advantages of Portfolio Optimization

Below mentioned are some of the major advantages of portfolio optimization:

  • Maximizing Return – The first and foremost objective of portfolio optimization is maximizing return for a given level of risk. The risk-return trade-off is maximized at the point on the efficient frontierEfficient FrontierThe efficient frontier, also known as the portfolio frontier, is a collection of ideal or optimal portfolios that are expected to provide the highest return for the minimum level of risk. This frontier is formed by plotting the expected return on the y-axis and the standard deviation on the x-axis.read more that represents the optimal portfolio. So managers pursuing the process of portfolio optimization are often able to achieve high returns per unit of risk for their investors. This helps with client satisfaction.Diversification – Optimal Portfolios are well diversified in order to do away with the unsystematic riskThe Unsystematic RiskUnsystematic risk refers to risk that is generated in a specific company or industry and may not be applicable to other industries or the economy as a whole.  There are two types of unsystematic risk: business risk and financial risk.read more or non-priced risks. Diversification helps in protecting investors against the downside in case a particular asset underperforms. The other assets in the portfolio will protect the investor’s portfolio from crashing, and the investor stays in a comfortable zone.Identifying Market Opportunities – When managers indulge in active portfolio management, they track a lot of market data and update themselves with the markets. This practice can help them identify opportunities in the market ahead of others and take advantage of those opportunities for the benefit of their investors.

Limitations of Portfolio Optimization

Below mentioned are some of the major limitations of portfolio optimization:

  • Frictionless Markets – The Modern Portfolio Theory, on which the concept of portfolio optimization is based, makes certain assumptions hold. One of the assumptions is that the markets are frictionless, i.e., there are no transaction costs, constraints, etc., that prevail in the market. In reality, this is often found not to be true. There are frictions in the market, and this fact makes the application of modern portfolio theory complicated.Normal Distribution – Another assumption under the modern portfolio theory is that the returns are normally distributed. It ignores the concepts of skewness, kurtosisKurtosisKurtosis in statistics is used to describe the distribution of the data set and depicts to what extent the data set points of a particular distribution differ from the data of a normal distribution. It determines whether the data is heavy-tailed or light-tailed.read more, etc., when using the return data as inputs. It is often found that the returns are not normally distributedNormally DistributedNormal Distribution is a bell-shaped frequency distribution curve which helps describe all the possible values a random variable can take within a given range with most of the distribution area is in the middle and few are in the tails, at the extremes. This distribution has two key parameters: the mean (µ) and the standard deviation (σ) which plays a key role in assets return calculation and in risk management strategy.read more. This assumption violation under the modern portfolio theory makes it challenging to use.Dynamic Coefficients – The coefficients used in the data for portfolio optimization, such as the correlation coefficientCorrelation CoefficientCorrelation Coefficient, sometimes known as cross-correlation coefficient, is a statistical measure used to evaluate the strength of a relationship between 2 variables. Its values range from -1.0 (negative correlation) to +1.0 (positive correlation). read more, can change as the market situations change. The assumption that these coefficients stay the same might not be true in all cases.

Conclusion

Portfolio Optimization is good for those investors who want to maximize the risk-return trade-off since this process is targeted at maximizing the return for every additional unit of risk taken in the portfolio. The managers combine a combination of risky assets with risk-free assets to manage this trade-off. The ratio of risky assets to risk-free assets depends on the risk the investor wants to take. The optimal portfolio does not give a portfolio that would generate the highest possible return from the combination. It just maximizes the return per unit of risk taken. The Sharpe ratio of this portfolio is the highest.

This has been a guide to Portfolio Optimization and its definition. Here we discuss the process of an optimal portfolio, limitations, advantages, and examples of portfolio optimization. You can learn more about portfolio management from the following articles –

  • Examples of Standard DeviationFormula of Portfolio VarianceCareer Options in Portfolio ManagementCompare – Portfolio Management vs Investment Banking