EMCDDA member states monitor and report cannabis potency according to the total concentration of delta-9-tetrahydrocannabinol (THC) in sample weight, to the nearest 0·1%. For the current analyses, we obtained the median THC levels in herbal cannabis and resin [35]. In contrast to survey and TDI data, the EMCDDA does not disclose any details on the underlying sources of THC data per country and year. While the THC data aim to be representative of the retail level, the agency acknowledges several methodological limitations that might render some data not representative. It can be assumed that the presented data are predominantly obtained from a sample of police seizures of cannabis [39]. For Germany, THC data were corrected and completed by the respective EMCDDA focal point [40].
