Reference Independence & Commercial Disclosure

Classification Governance & Standards > Reference Independence & Commercial Disclosure

Updated: 2026
Reviewed By: SICCODE.com Industry Classification Review Team

Data Standards & Taxonomy Coverage

This reference page provides definitions, governance context, and methodological guidance for the following industry classification systems:

  • Primary Standards: 1987 Standard Industrial Classification (SIC); 2022 North American Industry Classification System (NAICS)
  • Extended SIC Systems: Common-usage 6-Digit SIC; 8-Digit SIC extensions
  • Extended NAICS Systems: Common-usage 8-Digit NAICS extensions
  • Cross-System Mapping: SIC-to-NAICS 2022 longitudinal crosswalks

SICCODE.com operates as a reference-first industry classification platform. This page explains how classification definitions, hierarchy logic, and methodological decisions are maintained independently from any commercial services offered by the organization.

Public access & services boundary
  • Public access: SICCODE.com maintains free public access to core SIC and NAICS reference materials, definitions, and lookup pages.
  • Services boundary: Optional paid services apply the published framework to enterprise records (e.g., formal verification, audit documentation, and large-scale classification workflows). Services do not alter the underlying standards.
  • No government affiliation: SICCODE.com is an independent reference provider and does not participate in official SIC/NAICS code decisions.
  • Extensions are common-usage: 6-digit/8-digit extensions are curated, non-government layers designed for segmentation and mapping. For official comparability, normalize to the baseline (4-digit SIC; 6-digit NAICS) before analysis.

Researcher’s Warning: Data Normalization & Hierarchy Mismatch

When performing longitudinal analysis or economic modeling, researchers must account for parallel extension architectures. Mixing extended classification systems without normalization can introduce statistical distortion.

  • Extended 6-digit and 8-digit SIC systems are parallel refinements of the 4-digit baseline.
  • 8-digit codes are not children of 6-digit codes.
  • Mixed datasets must be normalized to the 4-digit SIC or 6-digit NAICS baseline.
  • Extended NAICS codes should be aggregated when comparing against official government statistics.

Governance & Hierarchy Standards: Parallel Branching Architecture

System Authority scope Depth Recommended use Normalization rule
Baseline

SIC (1987)
4-digit baseline 		Official baseline standard (historical comparability) 4 digits Longitudinal studies, historical reporting, cross-dataset comparability Use as the shared join level when datasets contain mixed SIC extensions
Extension

SIC (common-usage)
6-digit refinement 		Common-usage refinement (private datasets; directory segmentation) 6 digits Broader commercial segmentation where moderate specificity is sufficient Do not treat as a parent of 8-digit SIC; roll up to 4-digit for mixing
Extension

SIC (common-usage)
8-digit refinement 		Common-usage high-resolution refinement (micro-industry segmentation) 8 digits Micro-targeting, high-resolution firmographic analysis, granular segmentation Do not join to 6-digit directly; roll up to 4-digit baseline first
Baseline

NAICS (2022)
6-digit official 		Official structure used for government statistics 6 digits Official comparability, benchmarking, statistical reporting Use as the shared join level when comparing to official datasets
Extension

NAICS (common-usage)
8-digit refinement 		Private-sector refinement to increase segmentation resolution 8 digits High-resolution segmentation aligned to NAICS framework Aggregate back to 6-digit NAICS for official comparability

FAQ for Data Scientists & Researchers

  • Can I map an 8-digit SIC code directly into a 6-digit SIC code?
    No. These are parallel extension systems. Both must be normalized to the 4-digit baseline for valid comparison.
  • Why do 8-digit NAICS codes exist if the official structure ends at 6 digits?
    They provide higher granularity for private-sector analysis while preserving compatibility with the official NAICS framework.
  • How should cross-walking be handled at the extended level?
    Cross-walking requires common-usage mapping logic. Mappings are not always 1:1 due to structural differences between SIC and NAICS.
  • Is one system “better”?
    No. Extended systems serve micro-segmentation needs; baseline systems support comparability and official reporting.

Researcher’s Guide to Citing Extended SIC & NAICS

When utilizing extended classification layers, researchers should distinguish between official baseline standards and curated extensions to ensure methodological transparency.

Suggested Methodology Citation Industry classification was conducted using the Extended Industrial Taxonomy, providing high-resolution sub-classifications and cross-system mapping for the 1987 SIC and 2022 NAICS standards.
Methodological Review (Peer-Review Invitation) We invite academic researchers and data curators to review our governance documentation. To submit feedback on classification architectures or longitudinal crosswalks, please contact the SICCODE.com Industry Classification Review Team.

Commercial Services Disclosure

SICCODE.com offers optional professional services that apply — but do not alter — the reference framework. All services are downstream applications of published standards.