This article has quite a few sources: <a href="http:&#x2F;&#x2F;www.migrationpolicy.org&#x2F;article&#x2F;free-movement-europe-past-and-present" rel="nofollow">http:&#x2F;&#x2F;www.migrationpolicy.org&#x2F;article&#x2F;free-movement-europe-...</a>  And a more recent report: <a href="http:&#x2F;&#x2F;ec.europa.eu&#x2F;social&#x2F;BlobServlet?docId=11945&amp;langId=en" rel="nofollow">http:&#x2F;&#x2F;ec.europa.eu&#x2F;social&#x2F;BlobServlet?docId=11945&amp;langId=en</a>