https://www.eurofound.europa.eu/sites/default/files/ef_publication/field_ef_document/ef22040en.pdf
https://esg.wharton.upenn.edu/zicklin-center/zicklin-bright-index/
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/662744/State_of_the_Nation_2017_-_Social_Mobility_in_Great_Britain.pdf