Concordance between SITC Rev 2 at the 4-digit level and NAICS (1997)

      The basis for this concordance is the US import and export data in 1989, from the NBER 
website. The data sets contain trade data classified by 5-digit SITC Rev. 2 items and 6-digit 
NAICS industries. The 5-digit SITC Rev. 2 items are truncated into 4-digit subgroups. The 4-
digit SITC Rev. 2 subgroups are matched, for exports and imports separately, to the 6-digit 
NAICS industry with the highest trade value. If the export and import matches agreed, we 
accepted that match. If they disagreed, the match to the largest sum of exports and imports was 
accepted. In some cases, the NAICS industry listing was truncated to 5 or occasionally 4 digits to 
encompass most trade, and to avoid NAICS categories used only by the United States. In a few 
cases, preference was given to more specific NAICS categories that matched the SITC definition 
over catchall NAICS categories. 

The original NAICS contains some codes ending with ?X? or ?XX?. They were adjusted as 
follows:
SITC Rev. 2    Original NAICS      Adjusted NAICS
  0011                  11211X                     1121
  0014                  1123XX                    1123
  025                    1123XX                    1123
  0484                  31181X                     3118
  0611                  31131X                     3113
  0612                  31131X                     3113
  0613                  31131X                     3113
  3510                  22111X                     2211
  7132                  33631X                     33631