This working paper results from a collaboration with impact professionals from BII, EBRD, IDB Invest, and IFC and it invites like-minded investors to build a shared language for defining, claiming, and measuring market effects in private sector impact investing. It ends with a call to action, urging impact investors to think about how they can work more intentionally and effectively to drive market-level changes. 

We outline four high-level steps for investors to incorporate market effects into their impact assessments. These steps are not operational guidelines but can guide investors as they design investments and assess their impact. The aim is to spark dialogue within the impact investing community, without representing the official position of any institution.