The U.S. national debt grew significantly from 2001 to 2009, both in dollar terms and relative to the size of the economy (GDP), due to a combination of tax cuts, wars and recessions. Measured for fiscal years 2001–2008, Federal spending under President Bush averaged 19.0% of GDP, just below his predecessor President Bill Clinton at 19.2% GDP, although tax receipts were substantially lower at 17.1% GDP versus 18.4% GDP. Income tax revenues averaged 7.7% GDP under Bush, versus 8.5% GDP under Clinton. The sizable national debt increases during his administration represented a reversal from a sizable surplus projection by the Congressional Budget Office just prior to his taking office.