The THC content of different cannabis products has varied and continues to vary widely. The Forensic Science Service (FSS) regularly analyses drug seizures and indicates that new growing techniques since the 1990s have led to some new products, such as skunk, coming onto the market with average THC levels two or three times greater than for other cannabis products.
There is no accurate estimate available for the proportion of skunk available as a proportion of all cannabis used in the U.K. The FSS has little recorded information on the type of herbal cannabis encountered. However, anecdotal information from FSS scientists suggests that there has been an increase in "skunk" type cannabis in both police and customs seizures.