In this article, we analyze the impact of weights constraints in portfolio theory using the seminal work of Jagannathan and Ma (2003). They show that solving the global minimum variance portfolio problem with some constraints on weights is equivalent to use a shrinkage estimate of the covariance...

Despite portfolio construction based on expected utility theory and Markowitz mean-variance optimization having been the foundation of financial economic theory for more than 50 years, its practical application by financial advisors has been limited. Particularly troubling are the lack of a...

Based upon a Markowitz methodology, this paper considers use of commodities futures as assets to enhance portfolio diversification. A very simplistic methodological approach is chosen to allow various portfolio issues to be highlighted with data from the recent financial crisis. Naïve long-only...

A well-known pitfall of Markowitz (1952) portfolio optimization is that the sample covariance matrix, which is a critical input, is very erroneous when there are many assets to choose from. If unchecked, this phenomenon skews the optimizer towards extreme weights that tend to perform poorly in...

The central message of this paper is that nobody should be using the sample covariance matrix for the purpose of portfolio optimization. It contains estimation error of the kind most likely to perturb a mean-variance optimizer. In its place, we suggest using the matrix obtained from the sample...