The discretionary budget refers to the part of the federal budget which Congress debates and decides every year. The remainder of the federal budget is 'mandatory spending.' Discretionary spending has recently increased significantly, though the largest portion of the increase is due to increases in military spending. In FY2005, much of the increase can also be attributed to hurricane relief (see spike in 'domestic spending' that year); yet, this amount is less than spending on just the Iraq War in that year.

Source: Office of Management and Budget, Budget of the U.S. Government, FY2009, Historical Tables. Amounts are in budget authority, for fiscal years.