Former colonies are notoriously poor today. according to the cia world factbook, of the 40 poorest countries on earth in 2010, what percentage are former colonies of european nations?

According to the CIA world Fact book, out of the 40 poorest countries in the world in 2010, 84% of them were former colonies of European Empires.

These included world powers such as Britain, France, Spain, Netherlands etc.
The colonial powers used a vast network of shipping and logistics to exploit local resources which made European countries extremely rich.

Countries such as Spain imported Gold, Potatoes, Peppers from South America and sold them all over the world, while the British Empire used India's immense human capital for farming and cheap manufacturing.

Answer is mass marketing.