Studies in several countries show that the amount of gasoline purchased by consumers initially rises after the price of gasoline has fallen. There are many different gasoline companies that compete with each other to provide the most attractive price to consumers. Gasoline manufacturers will not expand their profit margins. Refining costs, distribution costs, and taxes, none of which varies significantly with oil prices, constitute a large portion of the price of gasoline.
Oil analysts predict that if the price of oil falls by half, the consumer' s purchase price for gasoline made from this oil will also fall by half.
Which one of the following, if true, would cast the most serious doubt on the prediction made by the oil analysts?