Every animal experimentation licence in Switzerland starts with an expected maximum severity, set when the licence is first submitted. But how closely does that expectation match what actually happens over the life of the project? By comparing prospective and retrospective severity classifications for all 2,325 licences active in 2023, this brief examines how often, and in which direction, initial severity estimates change.

Most licences (70.5%) keep the same maximum severity throughout their lifetime. Where classifications do change, downward reclassification is more common than upward: 17.8% of licences end up lower than initially expected, compared with 11.7% reclassified upward, most of which involve a shift from SD2 to SD3.

Importantly, the large majority of high-severity (SD3) animal uses (94%) occur in licences that already anticipated SD3 severity from the outset. Only a small share of SD3 use comes from licences that were not expected to reach that level, and even within those licences, SD3 use typically remains a small fraction of total use.

Patterns also vary by research purpose: applied research licences show the highest rate of upward reclassification (23.9%), while education and disease diagnostic licences show very few reclassifications in either direction. These findings offer a first systematic look at how severity estimates evolve after a licence is approved, and point to where refinement and reduction efforts are most likely to pay off.