The influence of economic parameters on the results in reserve estimate is mainly the change of time in zero of pretax net cash flow, that is, the change of economic life.

We should not forget that coal - whose reserves are estimated at 150 years versus 40-100 years for oil - can also be used to produce the building blocks for our favorite polymers.

Delayed or shelved exploration projects from offshore West Africa to the Canadian oil sands could lead to a supply crimp in the next few years if and when demand comes roaring back.