This difference probably reflects the fact that until 1989 most employees in communist East Germany were more or less obliged to become a member of the Confederation of Free German Trade Unions (Freier Deutscher Gewerkschaftsbund, or FDGB), a state-controlled mass organization for labour that lacked most of the characteristics of free trade unions (including bargaining autonomy, right to strike, etc.).
exploredata-ZA3700_VarV3 exploredata-ZA3700_VarV545