Algeria has a population of an estimated 44 million, of which the vast majority are Arab-Berber ethnically. At the outset of the 20th century, its population was approximately four million. About 90% of Algerians live in the northern, coastal area; the inhabitants of the Sahara desert are mainly concentrated in oases, although some 1.5 million remain nomadic or partly nomadic. 28.1% of Algerians are under the age of 15.