Two-panel figure. Top: share of COD entries per publication year in three formula classes (no carbon; carbon without hydrogen; carbon and hydrogen). The C-and-H class overtakes the no-carbon class in 1995. Bottom: absolute entry counts (log scale); no-carbon entries peak at 2,949 in 2003 and fall to 316 by 2024. Data: COD REST API counts, queried 2026-08-09 UTC.