"The estimated number of participants in the ibogaine subculture increased fourfold relative to the prior estimate of 5 years earlier, an average yearly rate of growth of approximately 30%."
Source
Alper, Kenneth R.; Lotsof, Howard S.; and Kaplan, Charles D., "The ibogaine medical subculture," Journal of Ethnopharmacology (Cagliari, Italy: International Society for Ethnopharmacology, January 2008), Volume 115, Issue 1, p. 20.
