The Tax Justice Network's Estimating the Price of Offshore Revisted report says that over $21 trillion has been squirrelled away in offshore tax-havens by 90,000 super-rich tax-cheats (0.001% of the world's population). The crime was abetted by a network of "enablers" from banks like UBS, Credit Suisse and Goldman Sachs.
Much of the money has been looted from the world's poorest countries, whose populations live in conditions of crushing poverty exacerbated by even more crushing international debt. The report estimates that if those countries' oligarchs and crime bosses were to pay their fair share of taxes that these debts could be settled. For example, Nigeria has lost £196b to tax havens -- while the country's national debt was about $37b as of 2011.
Heather Stewart has more in The Observer:
James Henry, former chief economist at consultancy McKinsey and an expert on tax havens, has compiled the most detailed estimates yet of the size of the offshore economy in a new report, The Price of Offshore Revisited, released exclusively to the Observer. He shows that at least £13tn – perhaps up to £20tn – has leaked out of scores of countries into secretive jurisdictions such as Switzerland and the Cayman Islands with the help of private banks, which vie to attract the assets of so-called high net-worth individuals. Their wealth is, as Henry puts it, "protected by a highly paid, industrious bevy of professional enablers in the private banking, legal, accounting and investment industries taking advantage of the increasingly borderless, frictionless global economy". According to Henry's research, the top 10 private banks, which include UBS and Credit Suisse in Switzerland, as well as the US investment bank Goldman Sachs, managed more than £4tn in 2010, a sharp rise from £1.5tn five years earlier.