Here are the numbers for U.S. discretionary spending (in trillions):
2008: $1.179
2009: $1.492
2010(est.): $1.247
2011(est.): $1.264
Source
Non-discretionary spending has increased dramatically due to massive increases in unemployment benefits payouts, thanks to the Republican Great Recession.
Right-wingers like to use spending as a percentage of GDP because it fits their agenda. If spending remains unchanged but GDP decreases, spending as a percentage of GDP increases, so it’s not an honest argument.