In Modern Portfolio Theory, what does the efficient frontier represent?

• A. The boundary of portfolios offering the highest expected return for a given level of risk.
• B. A random selection of assets that ignores diversification.
• C. A portfolio with the minimum possible variance for any return.
• D. A historical line plotting asset prices.

Answer: (B)

In Modern Portfolio Theory, the efficient frontier is the boundary of the set of portfolios that offer the best possible trade-off between risk and return: you get the highest expected return for a given level of risk (or the lowest risk for a given level of expected return). This boundary arises from optimizing across asset combinations and leveraging diversification to reduce unnecessary risk. Each point on the frontier is not improvable without accepting more risk or accepting less return; it represents an efficient choice given the available assets and their return, variance, and correlations. The idea isn’t about randomly picking assets or ignoring diversification—it’s about constructing portfolios that maximize the return for a given risk through careful asset mixing. It’s also not a single historical line of asset prices or a portfolio with minimum variance for every possible return; the frontier captures the best risk-return compromises across all feasible portfolios.