[Dynamics of the drug scene in Switzerland 1977-1990]

The registry of charges against users of illegal drugs in Switzerland is showing a steady increase from 1977 to 1990. Of course, the relation between the number of charges and the number of users is unknown and may vary in time and space. But it is shown here that the dependency of the data from the practice of the police can be circumvented with the help of a mathematical model and the distinction between first and subsequent charge. The least squares fit of the model to the data leads to an estimated time series of the number of illegal drug users that implies, with respect to 1977, the twofold in 1982 and the threefold in 1990.