Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
Analysis of shareholdings reveals that corporate directors generate positive alpha when they hold board interlocked stocks, where they are not an insider but a current co-board member is. In contrast, directors do not outperform when they hold inside stocks or other stocks unconnected to the board network. Analysis of trades shows that directors outperform when they buy or sell their own company's stock as insiders. They also outperform when they buy interlocked stocks. Results are similar for trades made before firm-specific information events. We also find limited support for the hypothesis that industry familiarity improves performance.