Big data will not change the world unless it is collected and synthesized into tools that have a public benefit. In this talk Sarah Williams will illustrate projects from her research lab, the Civic Data Design Lab @ MIT, that have transformed data into visualizations that have had an effect on policy reform. From her work on the Digital Matatus project in Nairobi Kenya, where she created the first map of the informal transit system, to her work on in Garment District in Midtown Manhattan, to more recent work investigating the Ghost Cities in China, Williams will show how collecting data, visualizing it, and opening up to anyone to use can leverage the power of data to create real policy change.