The 168th Organization Of Petroleum Exporting Countries (OPEC) Conference [Getty Images]

Bijan Namdar Zanganeh, Iran's petroleum minister, speaks to journalists ahead of the 168th Organization of Petroleum Exporting Countries (OPEC) meeting in Vienna, Austria, on Friday, Dec. 4, 2015. Oil headed for its fourth decline in five weeks as the Organization of Petroleum Exporting Countries looked set to leave its production ceiling unchanged at a meeting in Vienna on Friday. Photographer: Lisi Niesner/Bloomberg via Getty Images

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