This tends happen because payroll taxes and excise/other taxes function largely as a % of GDP since they are flat taxes that are rarely changed. That is more than half of overall federal taxation, which tends to pull the numbers to an average.
Clinton took taxes from 17% to 20%, and Bush took it from 20% back to 17%. Obama took it down to 15% and is likely going to raise it back to 17-18%.
Plan for eliminating the national debt in 10-20 years:
Specific cuts; defense spending: http://rolexian.wordpress.com/2011/01/03/more-detailed-look-a