Chapter 4 examines the form of contributory fault that involves a direct contribution by the investor: mismanagement. The first task is to justify recognition of this defence in international investment law, with the main justification being that investment treaties are not insurance policies for investments made in the face of foreseeable political risk. Then, after explaining what the investor’s contribution should look like, the focus turns to defining when it should be viewed as mismanagement. Various fault standards are surveyed, including recklessness and negligence, as determined through application of expected utility theory. Both are discounted, with the conclusion being that if the host state’s breach was objectively foreseeable, then the investor’s contribution equates to mismanagement. The harshness of this standard for the investor is smoothed over by the equation for apportioning liability between the investor and the host state. Arguing that the guesswork currently involved in apportioning liability should no longer be tolerated, a reason-based method is put forward. The concluding sections are dedicated to carving out mismanagement from other related legal concepts.