(OilPrice) Oil is fundamentally a depletable resource – once a barrel is extracted from the ground and burned, it is gone. Nevertheless, world oil production has continued to increase steadily for the last century and a half. Most economists attribute this to technological progress. Each year our methods for finding oil become more sophisticated, and our extraction methods more efficient. Unquestionably this progress has been quite remarkable, with oil now being produced by wells that begin a mile below the surface of the sea and proceed for several more miles through rock to get to the oil-bearing formations.