Population of the four major Yolngu towns (called "townships") ranges from approximately 1,000 to 2,000, including the permanent or semipermanent residents of the outstations or homeland centers serviced from the towns. The towns reflect their origins as missions, with a central area containing administration buildings and usually a church, as well as substantial well-constructed houses. Nearby, sometimes in the center and radiating away from the center, are the houses of the Yolngu people. This housing was at first of traditional shelter design, seasonally appropriate; subsequently, it was made of bush timber and corrugated iron; later, framed corrugated iron on cement slab was used. Increasingly houses have been built closer to standard Australian outback design, and still more recently they are of cement-block construction. At homeland centers, construction remains predominantly of bush timber or corrugated iron, with earth or sand floors, although some "kit houses" are now being erected. The largest center in the Yolngu area is the mining town at Nhulunbuy, with an estimated population of 3,500; fewer than 50 are Yolngu. In the other centers, non-Aboriginal residents are about 8 percent of the population and are mostly employees of the Yolngu towns and organizations.