https://www.hamiltonproject.org/assets/files/UnionsEA_Web_8.19.pdf
https://www.etui.org/sites/default/files/2025-06/Benchmarking%20Working%20Europe%202025%20-%20WEB.pdf
http://economics.mit.edu/files/12979
https://www.esri.ie/system/files/publications/SUSTAT95_0.pdf