Algeria is the largest country by land area; and by population, Nigeria is the largest. There are also two additional states whose independence is under dispute: Western Sahara and Somaliland. Africa has the second-largest population in the world, with an estimated 1 billion inhabitants. This constitutes almost 15% of the world’s population (2009 census). Over 1 000 official languages are spoken across the African continent; and the largest religious group is Islam, followed by Christianity.