United States. Bureau of Labor Statistics. "Business Sector - Appendix - Annual Data," in United States. Bureau of Labor Statistics. "Preliminary Fourth Quarter and Annual Averages for 2003," Productivity and Costs (February 5, 2004) : 19-19. https://fraser.stlouisfed.org/title/131/item/55780/toc/447151 , accessed on April 19, 2024.