Farming the U. is costly and very risky for farmers. A report by the U. Department of Agriculture estimates that farms in the U. cost $6 billion a year in energy costs and property taxes for households and property owners, not counting electricity and gas. In the United Nations' Grazing Costs for Humans study, the U. used $0. 13 per kilowatt-hour for coal, $0. 50 for electricity and the $2. 49 for gas. The U. consumes 2. 16 million tonnes of carbon dioxide a year, the fourth most of any country. The United States' reliance on coal plants also helps fuel its economy. More than 20 per cent of total U. emissions from coal are generated by the nation's mines and the top six industries collectively generate about a third. A recent analysis by the U. Chamber of Commerce found that the U. made $4. 3tn in the 2011 budget, more than twice the amount reported in any comparable measure except for its own military and its non-defense industries. Sophisticated policies are not making money here, the report said.