This post is mostly for my online class in Energy Economics. Here is the EIA data for worldwide total proved reserves of oil and natural gas, annual figures, divided by that year’s total production of each (with “dry natural gas” being used for the latter). According to some naive treatments, in 1980 the world had 27.5 years left of crude oil, and yet we didn’t run out in 2008, even though annual consumption had increased.
(In case you’re mystified: “Proved reserves” means reserves that have been located with reasonable certainty, and can be recovered under existing conditions. It would be a waste of manpower and other resources to go locate every last drop of oil on planet Earth; the industry only locates enough for a comfortable margin, and then finds more as demand warrants.)