What is the stability rule?

The stability rule prevents frequent changes to the classification of a unit whose mix of activities is almost balanced. Paragraphs 81 and 82 of the introductory guidelines state the rule. A unit may change its principal activity, but frequent changes would create inconsistencies between short term and longer term statistics. The rule is statistical only, and it does not determine a code for a specific reader.

Why is a stability rule needed?

Paragraph 81 states that units may change their principal activity, either abruptly or gradually, because of seasonal factors or because of a management decision to change the pattern of output. All such cases call for the classification of the unit to be changed. The difficulty is frequency. Frequent changes could result in inconsistencies between short term statistics, meaning monthly and quarterly statistics, and longer term statistics, making interpretation extremely difficult. A classification that flips with each quarter would describe the statistics more than it describes the unit.

Paragraph 82 states the purpose directly: to avoid frequent changes, a stability rule is necessary. Without such a rule, there would be apparent changes in the economic demography of the business population that would be no more than statistical artefacts. The rule is aimed in particular at units that engage in a mix of activities that is almost balanced, and are therefore subject to a higher risk of changes to the principal activity resulting from only small changes in the ratio of the activities involved. A small shift in the mix should not, by itself, rewrite the unit’s statistical identity.

How does the rule work?

Paragraph 82 states the working method. In the almost balanced cases, the ratio of activities over the previous two to three years should be taken into account when determining the principal activity of the unit. The rule therefore looks back over a period, rather than taking a single quarter or a single year in isolation. A unit whose mix has been almost even for two to three years is not reclassified on the strength of one period’s small movement. The look back period is stated as two to three years in the manual, and no shorter period is given as a general rule.

The same paragraph states the frequency limit. Changes in the classification of units for the purpose of statistical surveys are made not more than once a year, either at fixed dates or as information becomes available. More frequent changes would result in inconsistency between short term and longer term statistics. The once a year limit applies to classification changes for statistical surveys. It does not state a limit for other registers, and it does not state that a business register entry can never change. The register that holds an entry applies its own timetable, and the manual rule governs the statistical use of the classification.

What does the rule not do?

| Point | What the manual states |

|---|---|

| Trigger | Abrupt or gradual change, seasonal factors, or a management decision |

| Risk group | Units with an almost balanced mix of activities |

| Look back | Ratio of activities over the previous two to three years |

| Frequency | Classification changes not more than once a year for statistical surveys |

The table summarises paragraphs 81 and 82. The rule does not freeze a classification permanently, and it does not prevent a genuine change of principal activity from being recorded. It slows the recording, and it requires a longer view, so that the recorded change reflects a change in the unit rather than a fluctuation in the data. A reader who expects an immediate reclassification after a single period’s figures is expecting more than the statistical rule provides, and should ask the institute or register that holds the entry what timetable it applies.

What does this classification not decide?

A classification entry describes an activity for statistical purposes. The introductory guidelines give the limit in their own terms: the entry does not decide tax, social security, a collective agreement, licensing or funding eligibility for a specific unit. Those questions belong with the authority or register that decides them, under each question governing law. A reader who treats a statistical entry as a decision about eligibility is reading more into the entry than the classification states. Stated in the guardrail box, the same limit is repeated here, and the institute or register holding the record confirms the entry for a specific unit.

Where is the entry confirmed?

The checking sequence for this subject is short. First, the introductory guidelines for the rule as Eurostat published it. Second, the explanatory note for the category, for what the category includes and excludes. Third, the institute or register, for the entry actually held. No other source in this guide replaces any step in that sequence.

Look back over two to three years for an almost balanced mix, expect no more than one statistical change a year, and confirm the timetable with the institute or register that holds the entry.