The people of Nigeria are called Nigerians. The main ethnic groups, distinguished by different languages, are the Hausa, the Igbo (Ibo), the Yoruba, and the Fulani. The Hausa have been officially estimated to constitute 21 percent of the population; Yoruba, 20 percent; Igbo, about 16.1 percent; and Fulani, 12 percent. For information on the Fulani, see the chapter on Guinea in Volume 4.