Abstract: The concept of Cumulative Impact is one of the most controversial areas of construction claims. Conceived during a time when measurement of productivity was difficult, Cumulative Impact claims seek to account for additional labor costs which are not directly attributable to an individual change order, but are instead allegedly the result of the aggregated and “synergistic” effects to productivity of an excessive number of changes to a single contract. Despite case law supporting its existence, forensic schedule analysts continue to raise questions about this controversial claim. Does Cumulative Impact exist, or was the rationale flawed from inception? Is it possible to segregate productivity losses in order to define specific cumulative impact losses, or is a Cumulative Impact claim always a “total productivity loss” claim? And is there a way for a contractor to put together a claim that an owner will ever find acceptable? This paper will provide an overview of the theory behind these claims, and will address the arguments for and against Cumulative Impact claims, highlighting the key areas of the controversy.