Field entry, published 2026-11-03T00:00:00.000Z, updated 2026-11-03T00:00:00.000Z. Group: The four levels of ISCO-08

How do you read a four-digit ISCO-08 code?

To read a four digit ISCO-08 code, read it from left to right, treating each position as a step deeper into the hierarchy rather than as an independent number. The first digit names the major group, the first two digits together name the sub-major group, the first three digits together name the minor group, and all four digits together name the unit group. No digit stands alone. Each longer form contains the shorter form inside it, so the code tells a small story of narrowing scope in four short moves.

Step one: isolate the first digit

Cover the last three digits and look only at the first. That single digit places the code in one of the 10 major groups, the broadest family in the classification. At this stage you know the general field, and nothing more specific. Resist the temptation to guess the occupation from this digit alone, because a major group contains many sub-major, minor, and unit groups. The first digit is a starting point, not an answer.

Step two: add the second digit

Now uncover the second digit and read the first two digits as a pair. That pair names one of the 43 sub-major groups. The pair matters as a whole: the second digit does not carry a fixed meaning on its own, since the same second digit can occur under different first digits with different meanings. For a concrete published illustration, a code beginning with 22 sits inside 22 Health Professionals, which itself sits inside 2 Professionals. The opening pair therefore narrows the field from all professional work to health professional work, while still leaving many detailed groups ahead.

Step three: add the third digit

Uncover the third digit and read the first three digits together. That trio names one of the 130 minor groups, a cluster of related unit groups inside the sub-major family. The step from two digits to three is often where the subject matter starts to feel recognisable, because the cluster is narrower than a whole field. Even so, the minor group is still a group of occupations, not a single occupation. Keep moving if the question requires detail, and stop here only if the question is genuinely about a cluster rather than about a detailed group.

Step four: add the fourth digit

Uncover the final digit and read all four digits together. That full form names one of the 436 unit groups, the finest level in ISCO-08. Only at this point have you reached the most detailed group the classification offers. The fourth digit is therefore the digit that separates neighbouring unit groups inside the same minor group, and neighbouring unit groups are often the hardest to tell apart. That is why the explanatory note for the unit group deserves attention at this final step, more than at any earlier step.

A compact summary to keep beside a code

| Digits read | Level reached | Number of groups at that level | | First digit | Major group | 10 | | First two digits | Sub-major group | 43 | | First three digits | Minor group | 130 | | All four digits | Unit group | 436 |

Use that summary as a reading aid, not as a substitute for the group definitions. The digits tell you where a group sits, while the definition tells you what the group covers. Both are needed before a code can be used responsibly in a table, a comparison, or a description of work.

Three reading habits that prevent errors

First, always expand a short code before comparing it with a long one. A one digit figure and a four digit figure describe different levels, and comparing them directly will mislead. Second, never split a code into separate digits and interpret each digit in isolation, because meaning lives in the growing prefix, not in a lone digit after the first. Third, when two four digit codes share their first three digits, treat them as neighbours inside one minor group and look closely at their definitions, since the final digit may mark a distinction that matters for the question at hand. Those three habits turn a string of digits into a readable path, and they keep the reader inside the classification instead of guessing beyond it.

Sources checked

1. ILO ISCO-08

Back to the The four levels of ISCO-08 group or browse all occupations.