Risk Return in Modern Portfolio Theory
Specialists and experts make use of a number of tools to make easy the assessment of portfolios, one being the routine supposition. The routine supposition shows that the returns on a security are grouped around a sole number. Experts call this the central tendency towards the mean or average. This routine supposition allows an investor or portfolio manager to make choices of securities based on two different measures which are the anticipated return of the security, and the standard variation of the security's return.
Standard deviation is a measure of the anticipated deviation or unpredictability of returns in relation to the projected return. Ordinary deviation is a numerical measure of the spread of the security's returns. In most cases, the higher the standard deviation, the higher the total risk of a security or a portfolio.
The standard deviation of a portfolio is always under or equal to the weighted average of the standard deviations of the component securities. The standard deviation of a portfolio can be calculated from the standard deviations of the individual securities that make up the portfolio. Even if the return distributions of the individual securities inside a portfolio are not usually dispersed, as the whole number of securities held in the portfolio raises, the distribution of the portfolio's return leans towards regularity. The typical variation connected with the return on an asset reduces with time. As a result, the longer the analysis horizon is, the lower the standard deviation of the annualized returns over the horizon will be. Expanding the time horizon reduces the risk of a stock investment in relation to an asset that is not at risk. An insignificant estimate error can have a significant impact on the ending portfolio value if the analysis horizon is long.
