Structure of SIC Codes: Divisions, Major Groups, Industry Groups, and 4-Digit Industries (Plus Extended SIC)

Updated: 2026 | Reviewed By: SICCODE.com Industry Classification Review Team | Data Lineage: About Our Data Team

The Standard Industrial Classification system is a hierarchy used to organize establishment data at different levels of detail: Division, 2-digit Major Group, 3-digit Industry Group, and 4-digit Industry.

The most important distinction on this page is simple: official U.S. SIC is standardized through the 4-digit level, while Extended SIC codes at 6 to 8 digits are vendor-defined subdivisions built on top of those official 4-digit industries.

Official U.S. SIC: 4-digit anchor Extended SIC: vendor-defined detail

Structure of the Standard Industrial Classification

The structure of the Standard Industrial Classification (SIC) allows establishment data to be tabulated, analyzed, and published at the level of industrial detail that is most appropriate for the task.

  • Division: the broadest level of the hierarchy.
  • Major Group: the official 2-digit level used for broader rollups.
  • Industry Group: the official 3-digit level used for mid-level segmentation.
  • Industry: the official 4-digit level used for the most common standardized SIC classification.

In practice, many organizations anchor reporting and comparability on the official 4-digit SIC industry. Some private-sector datasets then add more detail inside selected 4-digit industries using Extended SIC Codes. Those extra levels can be useful for segmentation, but they should not be confused with the official U.S. SIC standard. :contentReference[oaicite:0]{index=0}

Governance note: Official U.S. SIC stops at 4 digits. Extended SIC codes may be highly useful in private-sector workflows, but they are not an official government classification standard. If extended codes are used, the source taxonomy should be documented for auditability and consistent interpretation.

How the SIC Hierarchy Works in Practice

The hierarchy lets users move between broader reporting and more detailed classification without losing the relationship between levels. That is one reason SIC remains useful for legacy data, market segmentation, and historical comparison.

Broad Reporting

  • Use Divisions for the highest-level business rollups
  • Useful when the goal is summary reporting or broad sector comparison
  • Best for simple overviews rather than precise targeting

Major Group Analysis

  • Use 2-digit SIC for broader industry families
  • Helpful for high-level benchmarking and category comparisons
  • Often used when 4-digit precision is not required

Industry Group Segmentation

  • Use 3-digit SIC for mid-level segmentation across related activities
  • Useful when 2-digit groups are too broad
  • Strikes a balance between comparability and detail

4-Digit Industry Classification

  • The most common official anchor for SIC-based classification
  • Best for standardized analysis and cross-dataset comparability
  • The right starting point when accuracy and consistency matter most

How “9” Works in SIC

When the digit 9 appears in the third or fourth position of a SIC code, it often indicates a residual category for establishments that are not elsewhere classified (NEC).

These NEC categories are important because they preserve the structure of the broader classification even when an establishment does not fit neatly into a more specific listed category. In practice, NEC groups can be less homogeneous than other industries, but they still provide a defined place for classification when a more exact match is not available. :contentReference[oaicite:1]{index=1}

SIC Structure Table

The table below shows the official U.S. SIC hierarchy by division alongside counts of Extended SIC codes used in vendor-defined private-sector taxonomies.

U.S. Government SIC Codes Extended SIC Codes
Division Title Major Group
2-digit		 Industry Group
3-digit		 Industry
4-digit		 Total 6-digit 7-digit 8-digit
A
01-09		 Agriculture, Forestry, Fishing 5 23 58 86 245 662 525
B
10-14		 Mining 4 20 31 55 98 410 362
C
15-17		 Construction 3 14 26 43 522 780 410
D
20-39		 Manufacturing 20 140 459 619 2,709 10,930 9,571
E
40-49		 Transportation & Public Utilities 10 37 67 114 424 732 451
F
50-51		 Wholesale Trade 2 18 69 89 2,082 3,315 1,757
G
52-59		 Retail Trade 8 41 64 113 1,288 1,835 859
H
60-67		 Finance Insurance, Real Estate 7 30 53 90 298 576 378
I
70-79		 Services 16 71 150 237 2,703 4,269 2,260
J
91-99		 Public Administration 8 22 28 58 156 412 356
Total 83 416 1,055 1,504 10,525* 23,921* 16,929*

* Extended SIC codes are continuously updated to reflect the marketplace. Definitions at the extended level are vendor-defined and may vary by source. :contentReference[oaicite:2]{index=2}

How to Use SIC Structure Correctly

The right level depends on the job you are trying to do. The hierarchy is most useful when each level is matched to the right kind of analysis.

1

Use Division or 2-digit SIC for broad reporting

Choose these levels when you need summary views, broad market rollups, or simple high-level comparisons.

2

Use 3-digit SIC for industry-group analysis

Choose 3-digit groups when you want mid-level segmentation across related business activities without jumping straight to 4-digit detail.

3

Use 4-digit SIC as the official anchor

Use 4-digit SIC when comparability, classification consistency, and standardized reporting matter most.

4

Use Extended SIC only with source documentation

Extended 6-digit, 7-digit, and 8-digit SIC can support more granular targeting, but the provider taxonomy should be named and retained so the classification remains interpretable.

Rule of thumb: when comparability and classification integrity matter, anchor on the official 4-digit SIC and use Extended SIC only as an added vendor-defined detail layer. :contentReference[oaicite:3]{index=3}