Here are some sites that discuss some related facts:
This one purportedly shows total taxes as a % of gdp to be around 30% for the U.S. I could not find data to support what I thought I hear regularly that the tax burden totals around 50%, but if you consider social security and medicare taxes, then the additional above 30% should approach at least 40% I am guessing, if those collections are not figured into the 30%.
http://www.oecd.org/dataoecd/6/63/1962227.pdf
Here are graphs that relate to tax revenue growth during the Coolidge, Kennedy, and Reagan tax rate cuts:
http://www.heritage.org/Research/Taxes/images/bg1086c4.gif
http://www.heritage.org/Research/Taxes/images/bg1086c6.gif
http://www.heritage.org/Research/Taxes/images/bg1086c10.gif
http://www.heritage.org/Research/Taxes/images/bg1086c11.gif
http://www.ncpa.org/sub/dpd/index.php?page=article&Article_ID=14054
I realize economists are political animals as well, and can look at the same figures but interpret them differently.
I do not think the Laffer curve has been tested, even with the very high marginal tax rates in the past, because they were only marginal rates, not overall rates, as Joe previously pointed out, so the overall average tax rate has never approached the point on Laffers curve that would indicate a complete failure of the economy. The reduction of the very high marginal rates do appear to clearly show a correlation between those reductions and increased revenues, so that it would appear those marginal rates were on the downward side of the Laffer curve. Our experience with the Laffer curve has been in its mid-range, so that tax rate cuts and increases do indicate effects, but not great enough to be totally convincing to all economists. But add to the fact that we know without a doubt that 0% tax rate would generate 0% tax revenues, and that we can project the likely effect of a hypothetical overall 100% tax rate, which we for sure do not wish to try, and that we have seen effects in the mid-range, it is enough evidence to show the existence of some kind of curve similar to Laffers.
At present, I tend to think we are below the peak of the Laffer curve and could raise top marginal rates slightly, not a great deal, and still raise more tax revenue, although the economy may suffer in accordance. However, I would of course favor more reductions of government programs and reduced spending instead of higher taxes. I disagree with Democrats in terms of not favoring more programs and increased spending as they do, but I may disagree with Republicans in terms of lowering tax rates much more if we insist on spending more money, as it only will increase the federal deficit further. And Republicans have been acting like Democrats lately in terms of more spending and programs. Both parties are irresponsible in the spending department.
I think this subject has about run into the ground. It is only one issue where one dimensional thinking exists, so I would prefer to go to another one. Thanks to those that seriously debated the thread so far. I think its been fun.