Demand elasticity for oil is low, about 0.5; so a 1 percent increase in oil price would cause a 0.5 percent decrease in consumption. That makes sense, since in the short run, it's hard for people to cut energy consumption, especially if they must drive to work. But, though numbers are hard to come by, elasticity of supply is much, much lower, for two reasons. First, oil production takes decades and billions in capital investment; producers cannot quickly increase or decrease supply. Second, oil producers form an international cartel, an organized mega-monopoly, which holds down production to drive up prices. Since they're already charging what the traffic will bear, they can't much raise prices to cover a tax.