The age of big data heralded a new understanding of the world in which analyzing the past allows one to predict future behavior. But are humans really soulless piles of numbers ? Data excel at revealing correlation among behaviors, but what about causation? After all, there is a difference between knowing something – what – and understanding it – why. This is where the social sciences – particularly ethnography – become critical, providing us a deep and insightful vision of the why behind the numbers. Through examples, we’ll explore how big data and ethnography come together – across sectors as varied as retail and global health – to provide even greater insights than ever imagined.