A district (Mongolian: сум, ᠰᠤᠮᠤ, sum, pronounced [sʰo̙m]; lit. "arrow"), is a second level administrative subdivision of Mongolia. The 21 Provinces of Mongolia are divided into 331 districts.
On average, each district administers a territory of 4,200 km2 (1,600 sq mi) with about 5,000 inhabitants, primarily nomadic herders. Its[clarification needed] total revenue is 120 million Tögrög, 90% of which comes from national subsidies.
Each district is again subdivided into bags (brigades; sometimes spelled baghs). Most bags are of an entirely virtual nature. Their purpose is to sort the families of nomads in the district into groups, without a permanent human settlement.
Officially, and occasionally on maps, many district seats (sum centers) bear a name different from that of the district. However, in practice the district seat (sum center) is most often referred to under the name of the district, to the point of the official name of the district seat (sum center) being unknown even to the locals.