Maxi Kindling et al. have published "The Landscape of Research Data Repositories in 2015: A re3data Analysis" in D-Lib Magazine.
Here's an excerpt:
This article provides a comprehensive descriptive and statistical analysis of metadata information on 1,381 research data repositories worldwide and across all research disciplines. The analyzed metadata is derived from the re3data database, enabling search and browse functionalities for the global registry of research data repositories. The analysis focuses mainly on institutions that operate research data repositories, types and subjects of research data repositories (RDR), access conditions as well as services provided by the research data repositories. RDR differ in terms of the service levels they offer, languages they support or standards they comply with. These statements are commonly acknowledged by saying the RDR landscape is heterogeneous. As expected, we found a heterogeneous RDR landscape that is mostly influenced by the repositories' disciplinary background for which they offer services.