Surveys in the United States indicate that at least 75% of the general public believe that global warming is a concern that needs to be addressed. However, there has been little action in the United States in support of this expressed concern. This is partly because most people do not understand that there is a link between vehicle fuel efficiency and global warming gases. Unlike criteria air pollutants, which can cause health problems and damage the environment and property, where public outcry and support has led to tough emission standards, there has been little public demand to do anything about global warming gases. As a consequence, Congress has done very little to improve vehicle efficiency since passing the CAFE standards in 1975. Vehicle purchasers generally rate fuel economy very low on their priority list for selecting a vehicle. It is also very difficult to market improved fuel efficiency to consumers, in part, because vehicle purchasers usually severely discount the value of the fuel savings. Although public research on the value consumers place on fuel savings does not exist, sources with proprietary data (manufacturers, J.D. Powers, etc.) indicate that the average consumer only values about the first 3 years, or 50,000 miles, of fuel savings.