United States. Bureau of Labor Statistics. "2002, 2003, and 2004 : 2002, 2003, and 2004, USDL - 06-2040,"
Total Factor Productivity in Major Industries
(December 6, 2006).
https://fraser.stlouisfed.org/title/9668/item/707639/content/pdf/prod5_20061206, accessed on September 9, 2026.