"Omnibus U.S. farm legislation--referred to as the farm bill--is renewed about every five years. Farm income and commodity price support programs have been a part of U.S. farm bills since the 1930s. Each successive farm bill usually involves some modification or replacement of existing farm programs. A key question likely to be asked of every new farm proposal or program is how it will affect U.S. commitments under the World Trade Organization's (WTO's) Agreement on Agriculture (AoA) and its Agreement on Subsidies and Countervailing Measures (SCM). The United States currently is committed, under the AoA, to spend no more than $19.1 billion annually on those domestic farm support programs most likely to distort trade--referred to as amber box programs and measured by the aggregate measure of support (AMS). The AoA spells out the rules for countries to determine whether their policies--for any given year--are potentially trade-distorting, and how to calculate the costs."
CRS Report for Congress, RS20840