https://www.tagesschau.de/inland/deutschlandtrend/deutschlandtrend-3368.html
https://www.socialeurope.eu/2017/06/mercron-franco-german-tandem-back-berlins-terms/
https://ec.europa.eu/info/sites/info/files/strategic_foresight_report_2020_1.pdf
https://pubs.aeaweb.org/doi/pdfplus/10.1257/jep.34.2.172