Described by the former British cabinet minister Vince Cable as "sunny places for shady people", tax havens are much maligned.
It's thought the total sum hidden away in low-tax, low-regulation jurisdictions around the world could be $21tn (£13.5tn) - as much as the total annual economic output of the United States and Japan combined.
Barack Obama and other world leaders have vowed to crack down on tax havens. The Organisation for Economic Cooperation and Development (OECD) has pressed for greater transparency about how they operate. The European Commission has called for greater information-sharing about tax deals by EU national governments.
Four experts talk to the BBC World Service Inquiry programme about why, despite this growing opposition, tax havens continue to prosper.