19th century. Large railway and road projects characterize the late 19th century. Railroads were emphasized in the colonial era, and roads in 'post-colonial' times. Jedwab & Storeygard find that in 1960–2015 there were strong correlations between transportation investments and economic development. Influential political include pre-colonial centralization, ethnic fractionalization, European settlement, natural resource dependence, and democracy. Many large infrastructure projects are underway across Africa. By far, most of these projects are in the production and transportation of electric power. Many other projects include paved highways, railways, airports, and other construction. Telecommunications infrastructure is also a growth area in Africa. Although Internet penetration lags other continents, it has still reached 9%. As of 2011, it was estimated that 500,000,000 mobile phones of all types were in use in Africa, including 15,000,000 "smart phones". Mining and drilling The mineral industry of Africa is one of the largest mineral industries in the world. Africa is the second biggest continent, with 30 million km2 of land, which implies large quantities of resources. For many African countries, mineral exploration and production constitute significant parts of their economies and remain keys to future economic growth. Africa is richly endowed with mineral reserves and ranks first or second in quantity of world reserves of bauxite, cobalt, industrial diamond, phosphate rock, platinum-group metals (PGM), vermiculite, and zirconium. African mineral reserves rank first or second for bauxite, cobalt, diamonds, phosphate rocks, platinum-group metals (PGM), vermiculite, and zirconium. Many other minerals are also present in quantity. The 2005 share of world production from African soil is the following: bauxite 9%; aluminium 5%; chromite 44%; cobalt 57%; copper 5%; gold 21%; iron ore 4%; steel 2%; lead (Pb) 3%; manganese 39%; zinc 2%; cement 4%; natural diamond 46%; graphite 2%; phosphate rock 31%; coal 5%; mineral fuels (including coal) & petroleum 13%; uranium 16%. Manufacturing Both the African Union and the United Nations have outlined plans in modern years on how Africa can help itself industrialize and develop significant manufacturing sectors to levels proportional to the African economy in the 1960s with 21st-century technology. This focus on growth and diversification of manufacturing and industrial production, as well as diversification of agricultural production, has fueled hopes that the 21st century will prove to be a century of economic and technological growth for Africa. This hope, coupled with the rise of new leaders in Africa in the future, inspired the term "the African Century",