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For most of the last century, cheap oil powered global economic growth. But in the last decade, the price of oil has quadrupled, and that shift will permanently shackle the growth potential of the world’s economies. The countries guzzling the most oil are taking the biggest hits to potential economic growth. That’s sobering news for the U.S., which consumes almost a fifth of the oil used in the world every day. Not long ago, when oil was $20 a barrel, the U.S. was the locomotive of global economic growth; the federal government was running budget surpluses; the jobless rate at the beginning of the last decade was at a 40-year low. Now, growth is stalled, the deficit is more than $1 trillion and almost 13 million Americans are unemployed.