Social enterprises and non-profit organizations often collect data to satisfy funders and create glossy reports, rather than to improve impact for the people they aim to serve. What if it didn't have to be this way? For the past 2 years, Acumen has been applying lean experimentation principles to the collection and use of social impact data. We call this new approach 'Lean Data." We've learned that social entrepreneurs can use new technologies to gain information about customers more quickly and efficiently than ever before, yielding powerful business insights about how they can make products, services and programs more meaningful for customers.