Because of the UDC's analytico-synthetic nature the number of subdivisions does not always reflect the true level of detail with which one can describe a document's content. Nevertheless, potential UDC users are often interested in the number of available classes in certain subject areas.
The pie chart on this page is a graphical representation of the distribution of subjects in the current MRF database (over 70,000 in 2012). The graph illustrates how much space pure sciences and technology, classes 5 and 6, occupy in the system. Another notable feature of the UDC concept distribution is the amount of common auxiliaries (coloured in grey) which are context-free concepts that are provided to be combined with all fields of knowledge.
The table below details the number of UDC subdivisions per subject area. The statistics reflect class distribution in the 2012 MRF database.