"The incidence of regular heroin use in the canton of Zurich started with about 80 new users in 1975, increased to 850 in 1990, and declined to 150 in 2002, and was thus reduced by 82%. Incidence peaked in 1990 at a similar high level to that ever reported in New South Wales, Australia, or in Italy. But only in Zurich has a decline by a factor of four in the number of new users of heroin been observed within a decade. This decline in incidence probably pertains to the whole of Switzerland because the number of patients in substitution treatment is stable, the age of the substituted population is rising, the mortality caused by drugs is declining, and confiscation of heroin is falling. Furthermore, incidence trends did not differ between urban and rural regions of Zurich. This finding is suggestive of a more similar spatial dynamic of heroin use for Switzerland than for other countries."
Nordt, C., & Stohler, R. (2006). Incidence of heroin use in Zurich, Switzerland: a treatment case register analysis. Lancet (London, England), 367(9525), 1830–1834. doi.org/10.1016/S0140-6736(06)68804-1