The article discusses how to evaluate the impact of blended finance projects on financial and development outcomes. It looks at different ways to measure the "additionality" of these projects, which means the extra benefits they provide beyond what would happen without them. The researchers suggest that additionality should be assessed before and after the projects take place, and that it depends on how well public and private interests are balanced. They also argue that the methods used to evaluate additionality will vary depending on the financial tools and types of benefits being considered. The article provides examples of different ways to assess additionality, which can help both evaluators and those involved in blended finance projects.