What a difference a year makes in the oil industry—or perhaps in this case 5 months.In July, crude oil prices peaked at $147/bbl and at this writing had plummeted to below $40/bbl. Questions have switched from How high can they go? to What is the new floor? Oil exporting countries such as Nigeria are reporting plunges in revenue, which have major repercussions for investments in health, education, and infrastructure.Who remembers that oil product prices based on $40/bbl crude was unacceptably high to consumers a few years ago? Now operators complain that prices that low are unsustainable because operating costs have risen and that $70-80/bbl is necessary if they are to develop unconventio...