Frequently policies and projects live or die by their perceived economic impact. The impact on jobs, economic product, employment income and tax revenues are quite rightly an important consideration when providing financial or other support to a project. In this regard, Economic Impact Studies can serve a valuable role in decision making. Frequently however, inputs and methodology can differ widely and the results of these studies are misunderstood. By highlighting some of the core methodological differences practitioners face in conducting these studies, we hope to both add transparency to the field and identify best practices along the way.