New development: From social impact bonds to impact bonds-an outcomes-based framework

Since their emergence in 2010 as social impact bonds (SIBs), impact bonds have significantly evolved from the prototype model. For example we now have 'development' impact bonds (DIBs) funding programmes in developing countries and 'environmental' impact bonds (EIBs) dealing with environmental challenges. Acknowledging this change, this article presents a framework to classify impact bonds according to the nature of the outcome pursued by the intervention. The article's main contributions are expanding the concept of cost saving and identifying three types of IBs by analytically linking outcomes to quantifiable gains.