United States. Bureau of Labor Statistics. "Business Sector - Appendix - Quarterly Data," in United States. Bureau of Labor Statistics. "Second Quarter 2002 [Preliminary]," Productivity and Costs (August 9, 2002) : 16-16. https://fraser.stlouisfed.org/title/131/item/55946/toc/447216 , accessed on April 23, 2024.