Traditionally, digital data repositories have been relatively basic online storage spaces for raw data, but with changing data demands, they are expanding to include complex functionality and specific analytic tools. New incentives for data sharing are driving data repositories to become more interconnected and interdependent just as more researchers seek trusted places to deposit their research data. Best practices and methods to assess data repositories' impacts and effectiveness, as well as to consider innovative ways to ensure their long-term financial viability, are critical for advancing scientific research across all domains. The Big Data Interagency Working Group (BD IWG) held a workshop, Measuring the Impact of Digital Repositories, on February 28 - March 1, 2017 in Arlington, VA. This report outlines BD IWG's recommendations and steps to accomplish R&D goals related to data repositories...