https://www.hamiltonproject.org/assets/files/UnionsEA_Web_8.19.pdf
http://www.ftseglobalmarkets.com/news/uk-pension-deficits-rise-to-£145bn-liabilities-at-record-high.html
https://www.ilo.org/media/545771/download
https://www.etui.org/content/download/36365/365328/file/WP+2019+07-wages-ST-WEB.pdf