https://www.socialeurope.eu/2017/06/understanding-productivity-puzzle/
https://www.federalreserve.gov/newsevents/speech/files/powell20200827a.pdf
https://www.brookings.edu/blog/up-front/2018/07/12/as-trump-twists-natos-arm-lets-run-the-math-on-defense-spending/?utm_campaign=Brookings%20Brief&utm_source=hs_email&utm_medium=email&utm_content=64421876
https://www.bruegel.org/2021/04/setting-europes-economic-recovery-in-motion-a-first-look-at-national-plans/