How do you read a one to one row?

A one to one row shows one NACE Rev. 2 class corresponding exactly to one class in NACE Rev. 2.1, and vice versa. The Eurostat manual states the definition in those terms, and gives the count as 354 NACE Rev. 2 classes. Even for a one to one row, the version, the direction, and the notes must be checked, because the row states a category relationship, and the notes state the scope that the relationship covers.

How is a one to one row laid out?

A one to one row, in the structure of the table as described in the manual, pairs a single old class with a single new class. The illustration below shows the structure of such a pairing, using code forms only, without asserting a particular mapping. A real row in the published table gives the old code and heading, the new code and heading, and the type. The illustration is a diagram of the row form, not a verified mapping, and it must not be quoted as a mapping for any particular class. A verified mapping is found only by reading the row for the class concerned in the published table, Version 1.05 as cited in the manual, or the current version on ShowVoc.

Row element	What the published row shows
Old class	One NACE Rev. 2 class code and heading
New class	One NACE Rev. 2.1 class code and heading
Type	1 to 1, exact correspondence in both directions
Illustration of the form only	Old class AA.AA, new class AA.AA, one row, one pairing

The form illustration uses placeholder codes, and the placeholders must not be mistaken for real codes. Real codes are four digit codes with a dot after the second digit, inside a division and group, with a section found by lookup. The illustration shows that there is one row, one old code, and one new code. It does not show which codes are paired, because that is the content of the published row for a particular class, and the content must be read there.

What must be verified beside the row?

Three checks sit beside the row. First, the version of the table must be noted. The manual cites Version 1.05 for the type counts, and the table on ShowVoc may carry a later version label. A type quoted from a table must carry the version of the table consulted, so that a later revision can be distinguished from the version cited in the manual. Second, the direction must be noted. A one to one correspondence is symmetric, so the direction does not change the type, but the direction must still be stated for clarity, because other row types are not symmetric in the same way, and a reading habit that states direction for every row avoids confusion when a different type is read next.

Third, the notes for the class in both versions must be compared. A one to one correspondence states that the scope is identical, and the notes are the evidence for that statement. The note for the old class and the note for the new class should state the same inclusions and exclusions, subject to editorial changes in wording that do not change scope. If the notes differ in scope, the row must be rechecked, because either the table version consulted differs from the version cited, or the note comparison has missed a boundary example. A one to one row must not be used to override a difference in the notes. The notes and the table must agree, and a disagreement must be resolved by checking the current table version and the current notes on ShowVoc and in the manual.

When can a one to one row support a direct comparison?

Double reporting, mentioned on the Eurostat overview page, provides a check for a direct comparison. Where data are tabulated by both versions in parallel for the same reference period, the figures for a one to one class should match, subject to rounding and to any other change in the production of the statistic. A mismatch in a double reported period is a signal to check the metadata, the table version, and the notes, before drawing a conclusion from the comparison. A match confirms the classification part of the comparison, and leaves the other metadata checks still to be done.

What does a one to one row not do?

A one to one row does not assign a code to a unit, and it does not confirm an entry. It states that two categories, one in each version, have identical scope. An activity that falls in the old category falls in the new category, by scope, but the assignment of a unit to that category for its principal activity is a separate step, made by the institute or register that holds the record, using the notes and the classification rules. A reader who follows a one to one row to a new code for a specific business has used a category relationship as if it were an assignment, and has skipped the assignment step. The row is a tool for comparing statistics and for tracing categories. The entry is confirmed elsewhere.

Read the published row for the class, note the table version and direction, compare the notes in both versions, and confirm any entry with the national statistical institute or the business register that holds the record.