"Because the percentage of addicts and consumers of illegal drugs in German penal institutions cannot be clearly quantified, the number of persons incarcerated as a result of violations of the Federal Narcotics Act (Betäubungsmittelgesetz) is frequently used. This estimate is relatively imprecise, however, because first of all it counts people who, although they have violated the law in connection with drugs, may not themselves have consumed any illicit substances, as could be the case, for example, with some dealers. Secondly, a large percentage of drug consumers are not taken into account because for example persons who are sentenced as a result of offences in connection with procurement of drugs are listed under other categories of violations against the Federal Narcotics Act in the statistics.
"As of 31 March 2010, there were a total of 8,841 persons (14.7% of all inmates) serving time in prison institutions as a result of violations of the Federal Narcotics Act (BtMG). Of these, 5.5% (511) were female, while 3.3% (294) were serving sentences as juvenile offenders. From 2006 (total: 64,512; BtMG: 9,579) to 2011, the total number of inmates increased by 6.9% whilst the number of inmates serving sentences due to BtMG offences decreased by 7.7% (Table 9.2). The number of inmates convicted for BtMG offences as a percentage of all inmates has remained constant for adults since 2006. For juveniles and young adults (in particular males) it is slightly decreasing (Statistisches Bundesamt 2011d)."

Source

German Reference Centre for the European Monitoring Centre for Drugs and Drug Addiction (Deutsche Beobachtungsstelle fuer Drogen und Drogensucht (DBDD)), "2012 National Report to the EMCDDA by the Reitox National Focal Point: Germany: New Developments, Trends and In-Depth Information on Selected Issues - Drug Situation 2011/2012" (Munich, Germany: DBDD, Oct. 2012), p. 170.
http://www.emcdda.europa.eu/h…
http://www.emcdda.europa.eu/a…