How do NACE, ISIC and national variants fit together?

ISIC, NACE, and national variants fit together as a hierarchy of derivations. ISIC is the international standard, maintained by the United Nations Statistics Division. NACE is the European derivation of ISIC, more detailed at lower levels, with the same items at the highest levels. A national variant is a derivation of NACE, in the European Union, or of ISIC, elsewhere, with additional detail below the shared levels for national use.

A code should be read at the level it belongs to, in the version it belongs to, and the hierarchy should be named in every citation that compares a code across levels, so that a reader does not mistake national detail for an international difference, or an international aggregate for a national category.

What is the hierarchy, level by level?

The hierarchy has three levels of derivation, and each level adds detail below the level above it. At the international level, ISIC Rev. 5 has 22 sections, 87 divisions, 258 groups and 463 classes, as the United Nations Statistics Division classification detail states. At the European level, NACE Rev. 2.1 has 22 sections, 87 divisions, 287 groups and 651 classes, as adopted, sharing the section and division counts with ISIC and adding detail at group and class level. At the national level, a variant adds detail below the class, or subdivides a class, for national use. Statistics Netherlands states that the Dutch SBI has five levels, with a maximum of five digits, that the first two levels are aligned with ISIC, that, with a few exceptions, the first four digits are identical to NACE, and that the fifth level is specific to the Netherlands. The pattern is the same. The detail is national, and it must be checked nationally.

How is a code placed in the hierarchy?

A code is placed in the hierarchy by naming its classification, its version, and its level, in that order. A four digit code can be an ISIC class, a NACE class, or the shared part of a national code, and the classification and version decide which. A five digit code, or a code with a letter suffix, is a national code, with the shared part to four digits and the national part below it, and it should be cited as such, with the national version named. A letter code is a section, and it should be cited with the version, because the section lettering changed in NACE Rev. 2.1, with the split of the former Section J and the shift that followed, as the Central Statistics Office states.

How are the three levels compared?

The three levels are compared by aggregating to the shared level, or by using a correspondence table, and the method should be stated. Aggregation means dropping the national detail and comparing at the division or group level where the categories match. Correspondence means consulting the table that shows the relationship between the two classifications or versions, and recording the mapping type for the pair. Eurostat describes correspondence tables between two different classifications as showing the relationship between all positions of the two classifications involved, and the same discipline applies to a national to NACE table, and to a NACE to ISIC table. Where the mapping is one to many or a split, the comparison should be made at the aggregate, or the split should be described, with the note for each category cited. Where the mapping is one to one, the revisions should still be named, because a one to one mapping in one pair of revisions may not hold in the next. A comparison that does not state its method cannot be repeated, and it should not be relied on.

Hierarchy level	Classification	Detail added
International	ISIC Rev. 5	Common frame, 22 sections, 87 divisions, 258 groups, 463 classes
European	NACE Rev. 2.1, derived from ISIC	More detail at group and class, 287 groups, 651 classes
National	National variant, derived from NACE or ISIC	Fifth level, letter suffix, or subdivision, national detail only

The table is a hierarchy map, not a directory. It names the three levels and the detail each adds, using the counts and examples verified in the pages consulted. It does not list every national variant, and it does not assert a timetable or a structure for any variant not verified in an institute publication consulted here. A reader who needs a named variant should open the institute publication for that country.

What is the role of the institute at each level?

The institute at each level is the holder for that level. The United Nations Statistics Division holds ISIC. Eurostat holds NACE, with the national statistical institutes of the European Statistical System. The national statistical institute holds the national variant, and the business register holds the entry for a unit in that variant. A question about ISIC meaning goes to the Division. A question about NACE meaning goes to Eurostat and the explanatory notes. A question about a national category goes to the national institute. A question about an entry goes to the register that holds it. A reader who asks the wrong holder will receive a referral, and the referral should be followed, not treated as a refusal. The hierarchy of classifications is also a hierarchy of holders, and the check should go to the holder for the level in question.

What does the hierarchy not decide?

The hierarchy does not decide the code for any unit, and it does not decide tax, licensing, funding, collective agreement or social security questions. It describes how three levels of statistical classification relate, for the purpose of comparing statistics. The entry for a specific business is confirmed with the national statistical institute or the business register that holds the record, in the national version the register uses. The meaning of a category at any level is confirmed in the publication for that classification and revision. The hierarchy is the frame for a comparison. The note is the meaning. The register is the entry.

Name the classification, version and level for every code, aggregate to the shared level for a comparison, and confirm a business entry with the institute or register that holds it.