The WSJ has an interesting article on how to think about the world's oil supply:  "But there is another way to visualize the future availability of oil: as a 'plateau.' *** In this view, the world has decades of further growth in production before flattening out into a plateau—perhaps sometime around midcentury—at which time a more gradual decline will begin. And that decline may well come not from a scarcity of resources but from greater efficiency, which will slacken global demand."  Take a look.

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