With a mandate, U.S. policy of ethanol tax credits designed to reduce oil consumption does the exact opposite. A tax credit is a direct gasoline consumption subsidy with no effect on the ethanol price and therefore does not help either corn or ethanol producers. To understand this, consider first the effects of each policy alone (a mandate and a tax credit). Although market prices for ethanol increase under each policy, consumer fuel prices always decline with a tax credit and increase with a mandate except when gasoline supply is less elastic than ethanol supply. To achieve a given ethanol price, the gasoline price is always higher with a mandate compared to a tax credit. A tax credit alone is an ethanol consumption subsidy but most of the benefits go to ethanol producers because ethanol is typically a small share of total fuel consumption. Fuel consumers benefit indirectly to the extent gasoline prices decline with increased ethanol production. With a tax credit or mandate, gasoline consumption declines but more so with a mandate (for a given ethanol price and production level). However, a tax credit with a binding mandate always generates an increase in gasoline consumption, the extent to which depends on the type of mandate. If it is a blend mandate (as in most countries outside the United States), the tax credit acts as a fuel consumption subsidy. Ethanol producers only gain indirectly with the increased ethanol demand resulting from the increase in total fuel consumption. Most of the market effects are due to the mandate with the tax credit only exacerbating the ethanol price increase and causing an increase in the gasoline price but a decrease in the consumer fuel price. For a consumption mandate (as in the United States), the tax credit is even worse as it acts as a gasoline consumption subsidy. Market prices of ethanol do not change, even as the price paid by consumers for gasoline declines (while gasoline market prices rise). A tax credit is therefore a pure waste as it involves huge taxpayer costs while increasing greenhouse gas emissions, local pollution and traffic congestion, while at the same time providing no benefit to either corn or ethanol producers (or in promoting rural development) and fails to reduce the tax costs of farm subsidy programs but generates an increase in the oil price and hence wealth in Middle East countries. These social costs are huge because the new mandate calls for 36 bil. gallons by 2022, to cost over $28 bil. a year in taxpayer monies alone. Even if the mandate is not binding initially, the elimination of the tax credit will cause the mandate to bind or the mandate can be increased so our results still hold.