2000 Census 3-Digit Industry and Occupation Codes. The 2000 Census codes were used to code industry and occupation for all jobs in the 2002 NLSY79 survey. Census published slightly revised codes in 2002, and these revised codes were used to code all jobs in the 2004 survey. Census issued another revision in 2003, and these codes were used for the 2006 survey. This attachment lists the 2000 codes, followed by the 2002 and 2003 codes; the 2002 tables note the slight differences from the 2000 list.