Transparency is not one of oil's properties. Corruption seems to rise to the surface wherever it is found. Is oil intrinsically dirty? "Oil rents have tended to impede democratization and have sustained a long line of authoritarian rulers -- from the Shah of Iran to Sani Abacha of Nigeria to the House of Saud to Saddam Hussein," the independent watchdog Catholic Relief Services (CRS) says in a report 'Bottom of the Barrel'. Several other reports point the same way. Oil and gas produce the biggest kickbacks after arms deals, Transparency International (TI) says in its latest report on bribery.