ABSTRACT We examine 1,948 share lockup agreements that prevent insiders from selling their shares in the period immediately after the IPO (typically 180 days). While lockups are in effect, there is little selling by insiders. When lockups expire, we find a permanent 40 percent increase in average trading volume, and a statistically prominent three‐day abnormal return of −1.5 percent. The abnormal return and volume are much larger when the firm is financed by venture capital, and we find that venture capitalists sell more aggressively than executives and other shareholders. We find limited support for several hypotheses that may explain the abnormal return, but no complete explanation.

ABSTRACT Many firms deploy takeover defenses when they go public. IPO managers tend to deploy defenses when their compensation is high, shareholdings are small, and oversight from nonmanagerial shareholders is weak. The presence of a defense is negatively related to subsequent acquisition likelihood, yet has no impact on takeover premiums for firms that are acquired. These results do not support arguments that takeover defenses facilitate the eventual sale of IPO firms at high takeover premiums. Rather, they suggest that managers shift the cost of takeover protection onto nonmanagerial shareholders. Thus, agency problems are important even for firms at the IPO stage.