One currently in vogue is that oil, priced in dollars, rises as the greenback falls. Working the other way, expensive oil widens the U.S. trade deficit, undermining the dollar.

• 当前流行的法则是，以美元计价的原油价格会随美元下挫而上涨。反过来说，昂贵的原油加剧了美国的贸易赤字，从而削弱美元。