The Congressional Budget Office issued a 42-page report entitled "Policy Options for Reducing CO2 Emissions." The study looks for, "The most efficient approaches to reducing emissions of CO2 involve giving businesses and households an economic incentive for such reductions. Such an incentive could be provided in various ways, including a tax on emissions, a cap on the total annual level of emissions combined with a system of tradable emission allowances, or a modified cap-and-trade program that includes features to constrain the cost of emission reductions that would be undertaken in an effort to meet the cap." The report comes to the conclusion that a carbon tax is in fact the "most efficient" option to reduce global warming. The belief is that such a tax would provide certainty on how much money would need to be spent to fight climate change. The CBO addresses the cost of a tax versus a cap-and-trade program and says, "The cost of implementing an upstream carbon tax is likely to be less than that of a cap-and-trade program (regardless of how allowances were initially allocated) because the tax could build upon an existing infrastructure."