United States. Bureau of Labor Statistics. "Nonfarm Business Sector - Appendix - Annual Data," in United States. Bureau of Labor Statistics. "First Quarter 1993 [Revised]," Productivity and Costs (June 17, 1993) : 16-16. https://fraser.stlouisfed.org/title/131/item/55830/toc/467876 , accessed on March 28, 2024.