Standing to sue under Rule 10b-5: A fresh look at the new investment doctrine

Several decisions have addressed the question of whether post-transaction a mendments or modifications and securities exchanges satisfy the purchase or sale requirements under Section 10(b) and Rule 10b-5. Nonetheless, there i s no constant and reliable approach to the question of what constitutes a n ew investment decision. This article analyzes the purchase or sale requirem ents under Section IO(b) and Rule 10b-5, then examines the recent decision in Department of Economic Development v. Arthur Anderson & Co., and finally looks at how economic models for risk analysis can lead to a consistent ap proach to the issue of what constitutes a new investment decision.