Barkin, Thomas I. "President's Message : What's Happening to Productivity Growth?," in Federal Reserve Bank of Richmond. "First Quarter 2019, Volume 24, Number 1," Econ Focus (Federal Reserve Bank of Richmond) (First Quarter 2019) : 3-3. https://fraser.stlouisfed.org/title/3941/item/583834/toc/527898 , accessed on February 5, 2023.