The 9th Annual State of Agile Survey is currently open for participants to share their adoption of Agile practices and processes for inclusion in the annual report.
Top-down implementation of agile is a commonly use approach for agile adoption in organizations. Alternative approaches exist, like implementing agile by stealth, using continuous improvement teams, starting with a quiet phase or taking baby steps by implementing a limited set of agile practices.
The 8th annual State of Agile Development Survey was announced at the Agile 2013 conference. Previous surveys have provided insight into agile adoption. You can participate in the survey, and get the data before it goes public.