Whether the price of oil is surging to new highs, as it is today, or slumping, as is predicted after a war in Iraq, there is one enduring constant: the dollar sign.
Oil trading, whether from Norway to the Netherlands, Britain to Bermuda, or Bahrain to Bangladesh, operates through the US greenback.
The oil-dollar nexus is one of the foundations of the world economy that inevitably filters through to geopolitics. Recycling so-called petrodollars, the proceeds of these high oil prices, has helped the United States run its colossal trade deficits. But the past year has seen the quiet emergence of the 'petroeuro'.
Effectively, the normal standards of economics have not applied to the US, because of the international role of the dollar. Some $3 trillion (£1,880 billion) are in circulation around the world helping the US to run virtually permanent trade deficits. Two-thirds of world trade is dollar-denominated. Two-thirds of central banks' official foreign exchange reserves are also dollar-denominated.
Dollarisation of the oil markets is one of the key drivers for this, alongside, in recent years, the performance of the US economy. The majority of countries that require oil imports require dollars to pay for their fuel. Oil exporters similarly hold, as their currency reserve, billions in the currency in which they are paid. Investing these petrodollars straight back into the US economy is possible at zero currency risk.