A good article. Useful data. In his 2013 book Globalisation in Africa Daniel Offiong mentioned that in every $1 that goes into Africa $10 leave the country.
I don't think the author's suggestions as a solution would work though. It is because the motive force of the capitalist system (led by corporations and especially Western governments and international instituions) is ignored. Corporations seek profit even if that happens at the account of people and the earth. A high enough rate of profit makes the system greased. Otherwise stagnation or crisis takes place. One should add of course the context of neocolonialism and the way it operates in making other countries dependent. The author, or probably the Guardian editor, has not used the appropriate terms to describe the situation: capitalism, imperialism (through institutions or violence), and neocolonialism, support of the status quo, including supporting coups (in the aftermath of the nominal independence) and co-opting uprisings or revolutions in poor countries.