The Markowitz mean-variance framework is the foundation of modern portfolio theory. One problem with this approach, however, is how sample covariance matrices tend to underestimate risk. Since the biases of optimized portfolios are closely related to eigenfactor portfolios, we present a...

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 the importance of board expertise by analyzing the role of “directors from related industries” (DRIs) on a firm's board. DRIs are officers and/or directors of companies in the upstream (supplier) or downstream (customer) industries of the firm. About 40% of firm-years in our...

We investigate the importance of board expertise by analyzing the role of “directors from related industries” (DRIs) on a firm's board. DRIs are officers and/or directors of companies in the upstream (supplier) or downstream (customer) industries of the firm. About 40% of firm-years in our...

With the proliferation of smartphone-based ridesharing apps around the world, traffic assignment with ridesharing is drawing increasing attentions in recent years. A number of ridesharing user equilibrium (RUE) models have been proposed, but most of them are formulated as mixed complementary...

Prior literature finds that earnings management is negatively correlated with institutional ownership. The question is whether institutional investors drive down earnings management of the firms they invest in, or they choose firms with lower earnings management. In this paper, we use the...

We study the relation between the market reaction to analyst recommendation changes and the structure of analysts' research portfolios. We find that analysts maintain more positive recommendations for stocks that belong to the quot;core industryquot; in their research portfolios, and are more...

This paper investigates the change of the credit spread volatility from 1993 to 2001. We find that credit spreads between junk grade corporate bonds and Treasury bond are significantly more volatile in the second half of this period when credit related securities become popular. However credit...