The average investor (where average is weighted by portfolio size) has no doubt considered correlations (and valuations and expectations and etc., etc.). The result of this has been the market portfolio. As above, Ken French's average invested dollar might be clearer. It's hard to believe that there's a major market participant which has not considered issues of portfolio construction.Random Walker wrote: Wed Mar 12, 2025 9:29 amI agree with you way more than you might think. I’m a big believer in market efficiency. In fact I’m pretty sure Fama states that TSM is always on the efficient frontier, and I think I’ve heard Larry Swedroe say that too. The only way I’ve been able to reconcile this in my mind is to distinguish between an efficient market and an efficient portfolio. Markowitz got a Nobel prize for Modern Portfolio Theory, and books like Roger Gibson’s Asset Allocation: Balancing Financial Risk and Larry Swedroe’s Reducing The Risk Of Black Swans show that combining low correlated assets in a portfolio make for more efficient portfolios. Gibson shows this by displaying how mixtures of uncorrelated assets move the potential outcomes of portfolios closer to the ideal northwest corner of a plot of return versus standard deviation. Larry shows this with potential portfolio outcomes that have same expected return but narrower standard deviations and smaller tails. In our portfolios, TSM is only one portfolio component. Adding other components with similar expected return and less than perfect correlation has a good chance of having created a more efficient portfolio when looking backwards at one’s investing results.exodusing wrote: Wed Mar 12, 2025 6:41 am
Your post appears to suggest a portfolio that's generally better than the market portfolio. If such a portfolio existed, why hasn't the market moved there? This does seem contrary to efficient markets.
Dave
MPT has essentially been superseded. The underlying insight (risk v. expected return) continues, but single factor, single time frame, simplistic definition of risk are just parts of a highly stylized model. See, for example, John Cochrane's https://www.johnhcochrane.com/research- ... ctor-world Larry, for all his virtues, is a fan of highly engineered portfolios which tend to have issues.
BTW, TSM is only one component of the market portfolio.