US Tax Revenue as a Fraction of GDP by Component

Quick post - while we are on the topic of taxes - I have been researching tax revenue as a percentage of GDP - and have found some great resources on the web i.e.- US Census Statistical Abstracts.
In the meantime before publishing my data I found a blog that does a nice job of presenting the numbers http://www.deptofnumbers.com/blog/.  I thought this would be informative until I can finish crunching the numbers.  

US Tax Revenue as a Fraction of GDP by Component

Looking at the components of the revenue is illuminating as well. The rise of Social Security tax revenue seems to neatly offset the decline in corporate tax and the miscellaneous taxes over the years. Personal income tax, always the largest source of federal revenue, also seems pretty range bound (albeit with a good deal of volatility). It'd be interesting to try to disentangle the effects of income, employment levels and marginal tax rates here. It's clear, however, that overall economic health plays a large role in how much income tax is collected. Peaks and troughs seem to correspond with recession start and end dates from visual inspection. ( from http://www.deptofnumbers.com/blog/2010/08/tax-revenue-as-a-fraction-of-gdp/)