" One key to African growth is what happens to commodity prices. Many African countries have long been and are still dependent on exports of “primary” commodities, mostly unprocessed minerals or agricultural crops. Botswana exports diamonds; South Africa, gold and diamonds; Nigeria and Angola, oil; Niger, uranium; Kenya, coffee; Côte d’Ivoire and Ghana, cocoa; Senegal, groundnuts; and so on. The world prices of primary commodities are notoriously volatile, with huge price increases in response to crop failures or increases in world demand and equally dramatic price collapses, none of which are easily predictable. "

― Angus Deaton , The Great Escape: Health, Wealth, and the Origins of Inequality