洛杉矶论文代写-现代投资组合理论。1952年，哈里•马科维茨(Harry Markowitz)在《投资组合选择》(Portfolio Selection)一文中发展并提出了现代投资组合理论(Modern Portfolio Theory, MPT)。MPT理论被认为是金融和投资领域最具影响力的经济理论之一。现代投资组合理论也被称为均值方差分析。该理论的基础是基于在特定风险水平下预期收益最大化的投资组合资产。数学框架中的风险称为方差。该理论认为，资产的回报和风险不是自我评估的，而是基于整个投资组合的总体风险和回报的贡献。
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 key elements of the MPT proposed by Markowitz (1952) are explained below.
Investors or the portfolio managers engage in the decision-making process based on the expected returns and the variance of the returns. The historical mean of the returns from an asset over a given time period derives the expected return from an asset. It must be noted that the terms mean and expected returns are interchangeable (Pok and Poshakwale, 2004).
The theory justifies that the portfolio selection is not based on the risk associated with the individual securities. The risk involved in the portfolio selection is based on the portfolio risk. The theory encompasses the combination of risky assets and expected returns from a portfolio which reflects relatively low risk. Conversely, it can be stated that it is quite possible to develop a portfolio with lower risk as compared to the sum of its counterparts.
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. This is presented below.