Is the Markowitz Theory the best Approach for all Portfolios? Explain Markowitz's train of thought about why investors should seek an efficient

Is the Markowitz Theory the best Approach for all Portfolios?

Explain Markowitz's train of thought about why investors should seek an efficient portfolio.

How Low Can Standard Deviation Go?

Is it true that the objective of efficient portfolio diversification is to determine a standard deviation that is lower than the individual security's standard deviation?

Is there a true risk-free portfolio?

In your opinion, is it possible to construct a risk-free portfolio?