Global passenger car production grew 2 percent in 2002, to 40.6 million units. The United States has one quarter of the cars in the world. Reflecting continued overcapacity in the industry, passenger car production outpaced sales by almost 2 million vehicles, or more than 5 percent. The United States, model-year 2001 light trucks emitted 2.4 times more smog-forming pollutants and 1.4 times more carbon than passenger cars. Driving a gasoline-powered car accounts for about 68 percent of the greenhouse gases emitted over the life of the vehicle, but producing and distributing the fuel on which it runs accounts for another 21 percent, while manufacturing the car itself contributes the rest. Automobile carbon emissions could be reduced significantly by boosting fuel efficiency. People outside the United States also use their cars less than Americans. The leaders in fuel economy are Honda, Hyundai, Volkswagen, and Subaru.