The Bill & Melinda Gates Foundation understands that rigorous evaluation is crucial for achieving the goals of the foundation and its partners. Rigorous evaluation allows for better decision-making, improved programmes and new innovations. The Gates Foundation has been a leader in the field of development impact evaluation, working with 3ie and other partners to fund impact evaluations and to disseminate results. Within its diverse programme areas, the foundation maintains a strong evaluation policy rooted in its core values of collaboration, rigour, innovation and optimism.