Tom, the efficient frontier failed in 1981 when Robert Shiller determined that volatility was the result of emotions and not changes in fundamentals. Since then many studies have tried to overturn his result to no avail. This means that the efficient frontier is a trade-off of long-term returns relative to short-term emotions. So for this reason I have abandoned the efficient frontier for building portfolios. It turns out that volatility is a measure of emotion and not a measure of risk. We will address this topic in more detail in a future post.