Why are the 1997 estimates of GDP by state different for SIC and NAICS?

There are several differences between the SIC and NAICS estimates, which may affect the industry estimates as well as the state totals. First, these are two different industry classifications, and as such, industries classified in one sector on SIC may be classified in another sector on NAICS. Second, the data sources and estimation methods used for NAICS may differ from those used to produce the SIC estimates. Finally, the NAICS-based estimates are consistent with national GDP while the SIC-based estimates are consistent with national gross domestic income (GDI). The difference between national GDP and national GDI is the statistical discrepancy, which, for the NAICS-based estimates, is allocated across all private-sector industries.