Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surface area.[7] With 1.4 billion people[1][2] as of 2021, it accounts for about 18% of the world's human population. Africa's population is the youngest among all the continents;[8][9] the median age in 2012 was 19.7, when the worldwide median age was 30.4.[10] Despite a wide range of natural resources, Africa is the least wealthy continent per capita and second-least wealthy by total wealth, ahead of Oceania. Scholars have attributed this to different factors including geography, climate,[11]corruption,[11] colonialism, the Cold War,[12][13] and neocolonialism. Despite this low concentration of wealth, recent economic expansion and the large and young population make Africa an important economic market in the broader global context. Africa has a large quantity of natural resources and food resources, including diamonds, sugar, salt, gold, iron, cobalt, uranium, copper, bauxite, silver, petroleum, natural gas, cocoa beans, and tropical fruit.