Security market line

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In Modern Portfolio Theory, the Security Market Line (SML) is the graphical representation of the Capital Asset Pricing Model. It displays the expected rate of return for an overall market as a fuction of systematic (non-diversifiable) risk (beta).

The Y-Intercept (beta=0) of the SML is equal to the risk-free interest rate. The slope of the SML is equal to the Market Risk Premium and reflects investors' degree of risk aversion at a given time.

When used in portfolio management, a single asset is plotted against the SML using its own beta and historical rate of return. If the plot of the asset falls above the SML it is considered to have a good rate of return relative to its risk, and vice versa if it falls below.