The Cash for Clunkers program provided incentives for automobile consumers, essentially lowering the price of the product. This lower price increased the quantity of cars demanded and sales dramatically went up. When the program was over and the price went back down, so did the car sales. This is a very accurate example of the change in demand through price. We can also see that the program was effective for the fuel efficient cars but not for the gas guzzlers. We can see that fuel efficient cars are a substitute for gas guzzling trucks because the decrease in price of the fuel efficient cars decreased the quantity demanded for the other. We can also see at the end of the article where automakers manipulated price again to decrease the quantity demanded so that they could replenish their inventory. What a good article for the topic of demand.