"If we look, for example, at the consumption of gasoline, it’s not declined. In fact it’s estimated to be near a record high in July," says Dr. Walden. "If we look at average speeds, they’ve gone down a little bit –- maybe half a mile per hour.

"If we look at the kinds of cars and trucks that Detroit and other auto makers are producing, not a lot of change there," he adds. "In fact, the 2006 model cars and light trucks are the heaviest and most powerful ever. The 2006 models also have lower fuel efficiency than models 20 years ago.

"So although people do complain about gas prices, we haven’t seen a lot of change yet in behavior," he concludes. "Some economists are thinking it might take $4, $5 a gallon gasoline or more to get people to make real changes."