This should be an interesting exercise...
On your 2011 return (or your software might give you a summary page with the information)...
Adjusted Gross Income
Taxable Income
Total Tax
Divide the Total Tax by the AGI and multiply by 100. Now, find your 2009 tax form and do the same thing. I've done a rough cut on our taxes for 2010 (still waiting on a bunch of forms) and it looks like we'll pay about 8%. By comparison, my 2009 was 2%.
Now, we did make about 25% more in 2010 than we did in 2009, so I'm willing to pay a little more