This is a public policy case-one of two HKS cases about Instiglio. In 2012, three recent graduates from Harvard Kennedy School (HKS) decided to start a nonprofit venture, Instiglio, in Medellin, Colombia. They wanted to introduce Social Impact Bonds (SIBs), but it was an untested idea not only in Colombia and other low to middle income regions but in established regions as well. This case provides the Colombia’s experience of HKS graduate and offers background of a SIB model (for an experimental social initiative, an investment criteria that provide the backing from the private investors to handle the financial risks). Along with other serious challenges, the two most critical decisions for the initiators were: (1) In presence of lack of data and competing demands, what could be the effective way to pick a project topic and (2) after deciding about the project topic, how to meet the desired requirements of regulators and investors through formulating an effective SIB model. While the second part of this case, “Devil in the Details: Designing a Social Impact Bond Agreement in Medellin,” is about statistics. Almost the same background, mentioned in this case, is used in the second part and provides a detailed analysis of existing challenges in formulating a SIB model. HKS Case Number 2026.0.