The most popular portfolio performance measures are the Sharpe ratio and alpha. While the Sharpe ratio is optimal under the CAPM assumptions of normal return distributions and unlimited borrowing at the risk-free rate, we find that it is not well aligned with investors' preferences in more...

Diversification across time means changing the asset allocation from one period to another. We show that diversification across time is inferior to a portfolio with the same average asset allocation, held constant over time: it leads to a lower geometric mean, implying that in the long-run it...

Standard mean-variance analysis is based on the assumption of normal return distributions. However, a growing body of literature suggests that the market oscillates between two different regimes – one with low volatility and the other with high volatility. In such a case, even if the return...

Even after more than six decades since the publication of the breakthrough article by Markowitz, the Mean-Variance framework is still the most commonly employed portfolio management tool. Yet, as portfolio managers know all too well, the optimal diversification and the induced performance are...

The Black-Scholes model and many of its extensions imply a log-normal distribution of stock returns. However, for holding periods of up to a year, the empirical return distribution (both conditional and unconditional) is not log-normal, but rather much closer to the logistic distribution. This...

The home bias is typically explained by various extra costs for foreign investments, such as higher transaction costs and information asymmetries. These costs have dramatically decreased over the last 15 years: the internet has revolutionized the global flow of information, accounting reports...