Effective June 14, 2001, data were reconstructed to reflect the switch from the Standard Industrial Classification (SIC) system to the North American Industry Classification System (NAICS).
Source: US. Bureau of the Census
US. Bureau of the Census, Total Business Inventories [BUSINV], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/BUSINV, February 8, 2016.