All Clinical compounds (n=3173), contain 937 ring systems (using ring systems from DataWarrior's scaffold calculator ). New ring systems added per decade account for approximately 30% of all ring systems present, in agreement with a recent analysis. However Clinical PNPs add more new ring systems than do Clinical NonPNPs, and the proportion of new ring systems is increasing over time in PNPs, but not NonPNPs (Figure ). PNP ring system novelty versus NonPNPs is consistent with their higher aliphatic and heteroaromatic ring counts (Table ).