https://rsf.org/en/ranking_table
http://fedtrust.co.uk/views-from-the-federal-trust/free-movement-and-migration/
https://theconversation.com/us-and-european-economies-depend-heavily-on-immigrants-decades-of-data-reveal-just-how-much-261508
https://www.bloomberg.com/politics/articles/2017-04-27/merkel-warns-against-u-k-illusions-in-hard-line-brexit-speech?utm_content=brexit&utm_campaign=socialflow-organic&utm_source=twitter&utm_medium=social&cmpid%3D=socialflow-facebook-brexit