The reply I give is " Because a third of the world does not want to walk or ride bicycles anymore "
Then give Matt Simmons's price comparisons re cups of expresso coffee,water and soft drinks etc.

Well, Econ 101 informs us that when demand exceeds supply the price rises until more is supplied and/or less is demanded. If an external agency (government) places an artificial/arbitrary ceiling on prices that is below the natural market price, the supply/demand mismatch will then manifest itself as a shortage. Then there is the whole issue of what 85M is...conventional oil, GTL/CTL, biofuels, etc? The non-conventional oil complementary/substitute liquids could very well be supplying the difference if they are not included in the 85M number. A good question is what is the World elasticity of demand for oil? How do country oil subsidies to consumers affect the resource depletion curves and the price? American consumers have a notoriously short and over-optimistic memory: Gasoline prices have tended to rise in a sawtooth fashion...going up quite a bit, then backing off by a quarter, a third, etc, then rising again to exceed the previous peak. During the price regression part of the sawtooth, consumers rejoice, do high-fives and tell themselves that the nay-sayers are idiots and do not understand the (fictional) 'free market',then they go back to driving large SUVs and driving like there is no tomorrow. Most people have no idea that oil was ~$29/barrel back in 2001. The vast majority of people have no concept of PO, and furthermore are ill-equipped to understand even the most basic precepts of PO, and even worse, they don't want to know. Watch 'Three Days of the Condor', and pay rapt attention to the final dialog. Last man (nation) standing is where we are going...Mad Max, anyone?