Africa is rich in natural resources such as minerals, timber and oil, but trade with the rest of the world is often difficult.
Factors include poor infrastructure, government instability, corruption and the impact of Aids on the population of working age.
Poorer countries and agencies such as Oxfam also argue that international trade rules are unfair and favour the developed world.
They say rich countries "dump" subsidised products on developing nations by undercutting local producers.
And they accuse the World Trade Organisation (WTO) of forcing developing nations to open their markets to the rest of the World but failing to lower rich countries' tariff barriers in return.
But the WTO says that low income countries receive special treatment, including exemption from some regulations that apply to richer nations.