The Institut der Wirtschaftsprüfer in Deutschland e.V. (Institute of Public Auditors in Germany, Incorporated Association - IDW) is a privately run organisation based in Düsseldorf established to serve the interests of its members who comprise both individual Wirtschaftsprüfers (German Public Auditors) and Wirtschaftsprüfungsgesellschaften (German Public Audit firms). The IDW was established on a voluntary basis rather than having been established under German law. In accordance with its Articles of Incorporation, the IDW does not operate as a commercial business and is a not-for-profit organisation. Membership as of 31 December 2009 was 12,979 full members, of whom 11,959 were German public auditors (87% of all German public auditors) and 1,020 were German public audit firms.