https://www.strategie.gouv.fr/sites/strategie.gouv.fr/files/atoms/files/fs-2019-na83-gains-monetaires-decembre.pdf
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/662744/State_of_the_Nation_2017_-_Social_Mobility_in_Great_Britain.pdf
http://www.ilo.org/wcmsp5/groups/public/—dgreports/—dcomm/—publ/documents/publication/wcms_548950.pdf