Differences between SML and CML:
1. The CML is a line that is used to show the rates of return, which depends on risk-free rates of return and levels of risk for a specific portfolio. SML, which is also called a Characteristic Line, is a graphical representation of the market’s risk and return at a given time. One of the differences between CML and SML, is how the risk factors are measured. While standard deviation is the measure of risk for CML, Beta coefficient determines the risk factors of the SML. The CML measures the risk through standard deviation, or through a total risk factor. On the other hand, the SML measures the risk through beta, which helps to find the security’s risk contribution for the portfolio.
2. While the Capital Market Line graphs define efficient portfolios, the Security Market Line graphs define both efficient and non-efficient portfolios i.e. the securities and portfolios that plot above the SML are undervalued and the ones below that are Overvalued. The securities and portfolio which plot on the SML are correctly value.
3. While calculating the returns, the expected return of the portfolio for CML is shown along the Y- axis. On the contrary, for SML, the return of the securities is shown along the Y-axis. The standard deviation of the portfolio is shown along the X-axis for CML, whereas, the Beta of security is shown along the X-axis for SML.
4. Where the market portfolio and risk free assets are determined by the CML, all security factors are determined by the SML.
5. Unlike the Capital Market Line, the Security Market Line shows the expected returns of individual assets. The CML determines the risk or return for efficient portfolios, and the SML demonstrates the risk or return for individual stocks.
The SML shows the required return on the security / portfolio based on its systematic risk. If the expected return on the security is higher than the required rate, then security is Undervalued and vice versa.