Table 2. Example from the ATC code hierarchy.

Level	Example	In data
Main group	N, Nervous system	17
3rd level subgroup	N02B, Other analgesics and antipyretics	219
4th level subgroup	N02BE, Anilides	503
Full code	N02BE01, Paracetamol	1063

The last column of the table shows how many different codes appear in the current data set for each code level.