Here are some useful links to research I have been involved in producing:
Language Trends survey 2012 (primary and secondary) published by CfBT
Languages: the State of the Nation, February 2013, The British Academy
Data on the link between language learning and social advantage/disadvantage – as presented at the Language World conference, March 2012 The Languages Gap
Lessons from abroad: international review of primary languages, published by CfBT
FE Trends survey 2011, a survey with FE Colleges in 2011. CfBT Education Trust, CILT Cymru, SCILT and Northern Ireland CILT.
The economic case for language learning and the role of employer engagement, published by CfBT in association with the Education and Employers Taskforce, Business for New Europe and the Association of School and College Leaders
And here is an article by Professor James Foreman Peck, who worked on the ELAN project, about the contribution of language skills to exporting and productivity. Costing_Babel