United States. Bureau of Labor Statistics. "Business Sector - Appendix - Quarterly Data," in United States. Bureau of Labor Statistics. "Second Quarter 2003 [Preliminary]," Productivity and Costs (August 7, 2003) : 18-18. https://fraser.stlouisfed.org/title/131/item/55776/toc/446910 , accessed on May 1, 2024.