1952年，哈里·马科维茨(Harry Markowitz)在《金融期刊》(the Journal of Finance)上发表了《投资组合选择》(Portfolio Selection)，提出并提出了现代投资组合理论(MPT)。MPT被认为是金融和投资领域最具影响力的经济学理论之一。现代投资组合理论也涉及均值-方差分析。该理论的基本原理是基于投资组合资产，在该资产中，在特定的风险水平下，预期收益最大化。数学框架中的风险被称为方差。该理论认为，资产的回报和风险不是自我评估的，而是基于整体风险的贡献和整个投资组合的回报。该理论的发展目标是构建一个投资组合，以最大化与可接受风险水平一致的预期回报。在这方面，马科维茨打算通过评估资产回报的方差来衡量和量化投资风险。在MPT的基础上，确定了两种股票收益的风险。经济衰退、利率冲击和战争等市场风险的系统性风险不容易分散(普菲菲尔曼、罗杰和布尔赫尼科娃，2016)。非系统风险是特定的风险，因为它是特定于个股的。单个股票的非系统风险可以通过增加投资组合中的股票数量来实现多样化

Harry Markowitz developed and propounded the Modern Portfolio Theory (MPT) published in the Journal of Finance in 1952 under the essay “Portfolio Selection”. The MPT is considered to be one of the most influential economic theories in the field of finance and investment. The modern portfolio theory is also referred to the mean-variance analysis. The fundamental of the theory is based on the portfolio assets in which the expected return is maximized for a specified level of risk. The risk in the mathematical framework is termed as variance. The theory suggests that the return and risk of an asset are not self-assessed but is based on the contribution of the overall risk and return of the entire portfolio. The theory is developed with the goal of fabricating a portfolio that is desired to maximize the expected returns which are consistent with the acceptable risk level. In this regards, Markowitz intended to measure and quantify the investment risk by the assessment of the variance of the return of an asset. Based on the MPT, two types of risks for individual stock returns have been identified. The systematic risks which are the market risk such as recessions, interest rate shocks and wars are not easily diversified (Pfiffelmann, Roger and Bourachnikova, 2016). The unsystematic risks are the specific risk as it is specific to individual stocks. The unsystematic risk for individual stocks can be easily diversified by increasing the number of stocks in the portfolio

The portfolio managers are alarmingly learning the key components of the MPT in order to manage risk and maximize its return. The main of this theory is that it ensures that the portfolio managers are able to derive the greatest potential return coupled with least risk. A portfolio manager through this theory is able to measure the relationship between the numerous types of investments (Shipway, 2009). In this way, the portfolio managers are able to compare and contrast between the risks and returns of the portfolio assets and investments which would help them to reduce risk and sustain maximum returns. MPT is regarded as a financial self-defense for the portfolio managers in which diversification is the way to smooth out the rough edges of the returns on investment. The basic idea of the MPT is based on the efficient portfolio which represents the investment opportunity set based on expected portfolio return and portfolio risk