United States. Bureau of Labor Statistics. "Nonfarm Business Sector - Appendix - Quarterly Data," in United States. Bureau of Labor Statistics. "Private Business, Nonfarm Business, and Manufacturing Sectors : Fourth Quarter 1980 and Annual Averages for 1980," Productivity and Costs (January 30, 1981) : 16-16. https://fraser.stlouisfed.org/title/131/item/55899/toc/437726 , accessed on April 19, 2024.