The basis of public finance statistics: the shell concept
The shell concept model is the frame for the integration of public budgets and public funds, institutions and enterprises.
The model includes a core consisting of the core budgets of the Federation, Länder, municipalities / associations of municipalities and social security funds. The middle layer comprises the extra budgets. The core budgets and extra budgets together form the overall public budget. This includes the EU shares which can only be assigned to the aggregate rather than to either of the two areas.
The outer layer contains any other public funds, institutions and enterprises.
More information is available in the methodological paper "Terms of the statistics of public finance and public service personnel".