Sample covariance matrices tend to underestimate the risk of optimized portfolios. In this article, we identify special portfolios, termed “eigenportfolios,” that capture these systematic biases. Further, we present a methodology for estimating eigenportfolio biases and for adjusting the...

We investigate whether the widespread adoption of online visits after the COVID-19 shock has been associated with higher analysts' forecast errors. Using a difference-in-differences methodology, we find a positive association between online mode and analysts' forecast errors. We further discuss...