The Price Elasticity of Demand for Gasoline is 0.7
This item in the Christian Science Monitor [h/t to Jack], written long before Katrina struck the Gulf Coast, gives many examples of how people in Europe have adjusted to higher gasoline prices.
And here is the basis for the elasticity estimate (in absolute value):
On average, 60 percent of the price European drivers pay at the pump goes to their governments in taxes.
... "Societies adjust over decades to higher fuel prices," says Jos Dings, head of Transport and Energy, a coalition of European environmental NGOs. "They find many mechanisms."
Chief among them, say experts, is the habit of driving smaller and more fuel-efficient cars.
"There is really good evidence that higher prices reduce traffic," says Stephen Glaister, a professor of transportation at London's Imperial College. "If fuel prices go up 10 percent ... fuel consumed goes down by about 7 percent, as people start to use fuel more efficiently, not accelerating so aggressively and switching to more fuel-efficient cars. It does change people's behavior."And now, after Katrina and the big jump in gasoline prices, lets see how the quantity demanded adjusts. Even in the short run, the quantity demanded at higher prices will have to fall -- the supply curve has shifted sharply to the left.
After all, demand curves are downward-sloping; people respond to incentives.