Identifying firm connections by shared analyst coverage, we find that a connected-firm (CF) momentum factor generates a monthly alpha of 1.68% (t = 9.67). In spanning regressions, the alphas of industry, geographic, customer, customer/supplier industry, single- to multi-segment, and technology momentum factors are insignificant/negative after controlling for CF momentum. Similar results hold in cross-sectional regressions and in developed international markets. Sell-side analysts incorporate news about linked firms sluggishly. These effects are stronger for complex and indirect linkages. Consistent with limited investor attention, these results indicate that momentum spillover effects are a unified phenomenon that is captured by shared analyst coverage.

We show that opportunistic insiders can be identified through the profitability of their trades prior to quarterly earnings announcements (QEAs) and that opportunistic trading is associated with various kinds of firm or managerial misconduct. A value-weighted trading strategy based on (not necessarily pre-QEA) trades of opportunistic insiders earns monthly four-factor alphas of over 1%, which is much higher than in past insider trading literature and substantial and significant even on the short side. Firms with opportunistic insiders have higher levels of earnings management, restatements, US Securities and Exchange Commission enforcement actions, shareholder litigation, and executive compensation. These findings suggest that opportunism is a domain-general trait.