Iraq shakes up rankings of oil nations. Who's on top?

When Iraq raised its estimate of proven oil reserves Monday, the world had to revise the list of nations with the most reserves. Not counting Canada's oil sands, here's a look at the new Top 5 nations:

4. Iran: 137.6 billion barrels

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    Iran's President Mahmoud Ahmadinejad (center, white jacket) toured Iran's first offshore oil platform in the Caspian Sea in 2009. A major oil exporter, Iran has limited oil-refining capacity.
    SHANA / AP / File
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The Islamic republic was knocked down to No. 4 with Iraq's new estimates of reserves. Several large oil companies, including BP, have reduced purchases of Iran's oil to comply with new international sanctions aimed at punishing the country for its purported pursuit of nuclear weapons.

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