Time series of any statistical data for Germany have considerable restrictions in
comparability. First of all, the German reunification in 1990 led to substantial territorial
changes, thus data prior to 1990 usually only covers the territory of the ‘old’ Federal
In addition, the German classification of economic activities of the year 1979 has
been revised considerable in 1993. Later revisions (1993, 2003 and 2008) are of minor
relevance. Data for 1993 and 1995 are still based on the older classification.