OpenAIRE has released Towards a Competitive and Sustainable Open Access Publishing Market in Europe.
Here's an excerpt:
Without intervention, immediate OA to just half of Europe's scientific publications will not be achieved until 2025 or later. Readers in academia have greater access, to more content, than ever before. Despite this, the majority of publications arising from public investments in research remain in accessible to the public, and the growth of OA appears to be slowing.
This study considers the economic factors contributing to the current state of the open access publishing market, and evaluates the potential for European policymakers to enhance market competition and sustainability in parallel to increasing access.