Capital flight is now known to extract substantially more cash from the developing world than is sent there in development assistance. A new fact sheet on capital flight has been produced by a range of NGOs headed by European umbrella NGO Eurodad. As it notes:

This fact sheet provides statistics, explanations and links that Eurodad members can use to understand and advocate on capital flight, the process whereby individuals or companies deposit funds and assets offshore. For each dollar that goes to the South in terms of aid, more than 7 dollars come back to the North through illicit proceeds. This flow of resources out of developing countries creates deficits, increases dependence on aid, makes recipients vulnerable to conditionality and renders debt cancellation less worthwhile. European NGOs have a responsibility to popularise this issue and to press their governments to introduce regulation for tax havens and companies to ensure that wealth can be retained and used for development purposes.

That's why this issue is so important. There are few shorter explanations of the issue than this fact sheet. I recommend it and the full report from which it is taken.