Martin Lipton is a founding partner of Wachtell, Lipton, Rosen & Katz, specializing in mergers and acquisitions and matters affecting corporate policy and strategy. This post is based on a Wachtell Lipton memorandum authored by Mr. Lipton. An important new study by Ed deHaan, David Larcker and Charles McClure, Long-Term Economic Consequences of Hedge Fund Activist Interventions, has found that on a value weighted basis, long-term returns are “insignificantly different from zero.” And, nearly all of the positive long-term returns are concentrated in companies that are acquired in the two-year period following the activist attack.