"Keeping Pace with K-12 Online Learning 2016" marks the thirteenth consecutive year Evergreen has published its annual research of the K-12 education online learning market. The thirteen years of researching, writing and publishing this report represents a time of remarkable change. There has been a constant presence that has become the backbone, supporting the growth and success of online learning--the array of organizations that supply online courses, online teachers, digital content and tools to schools. The number and breadth of types of suppliers has changed and grown as the demand for broader and deeper services has increased. Suppliers range from schools that supply regions or whole states, to stand-alone "intermediate" suppliers that provide online courses and related services to schools, to vendors who develop courses and content and deliver their courses directly to schools or distribute them through intermediates. "Keeping Pace with K-12 Online Learning 2016" focuses on these suppliers of online learning and reports on levels and types of activity, including online course enrollments, types of enrollments and number of students involved in online learning. [For "Keeping Pace with K-12 Digital Learning" (2015 edition), see ED570125.]