The Congressional Budget Office released its report Effects of a Carbon Tax on the Economy and the Environment on May 22, finding that a carbon tax could raise significant federal revenue. A 2011 report had estimated that a $20 per ton tax as part of a cap and trade system could create up to $1.2 trillion in revenue in the first decade. While it praised progress, the report warned that overall environmental impact would not be substantial since the U.S. accounts for less than one-fifth of worldwide emissions. The study also found that the tax would increase production costs on certain industries such as electricity; low-income households would be impacted most since a greater portion of their income is spent on affected products and services.