Definition
Skolverket does not publish results when the reported group comprises fewer than 15 students. The purpose is to protect individual students' identities — known as statistical confidentiality (statistisk sekretess).
In Skolkoll's data, this means the value is null. On the website it is shown as "—" or "Data unavailable".
Statistical confidentiality applies to all metrics: merit value, teacher certification, upper secondary eligibility, survey results and more. It is most common for:
- Small schools with few graduating students
- Breakdowns by gender or background
- Individual subject results
How to interpret
null ≠ poor results. This is the most common misunderstanding. Missing data means the group was too small to publish — not that the school is performing poorly.
Aggregate upwards. If an individual school is missing data, you can often find figures at:
- Municipal level — all schools in the municipality combined often produce large enough groups.
- Provider level — all schools run by the same provider combined.
Check the trend. If data existed last year but is missing this year, the group has probably shrunk below 15 students. This may be due to declining enrolment, not deteriorating results.
Quality flag. Skolkoll marks schools with limited data using the quality flag secret_limited. This helps you quickly identify which schools have confidentiality restrictions.
Common mistakes
- Interpreting "Data unavailable" as a poor result. It is statistical confidentiality — not a lack of quality.
- Excluding schools without data from comparisons. If you rank schools and exclude those without merit value data, you may miss the smallest schools, which can have entirely different characteristics.
- Overlooking that multi-year data may yield values. Even if a single year is missing, three- to five-year averages can sometimes be calculated if the group was large enough in some years.