The point is that the top 40% pay 106.1% of the income taxes and the bottom 40% actually have a negative income tax rate due to refundable tax credits. That concerns me greatly. A little over 50% of the taxpayers pay almost all of the income taxes. When that number falls below 50%, the poor will simply vote to take money from the wealthy and redistribute that wealth.
1. That chart is not just income tax, it's all federal taxes.
2. It's impossible to have more than 100% of something.
3. The Top 40% pay the most tax because they have the most money. Do you expect 10% of the income to pay 90% of the taxes?
4. The people that benefit most from the deal *should* pay more.
5. If you read further into the document, you'll get to the part where they discuss trends. Trends about tax rates, income growth, etc, etc. Bottom line: the tax rates for most Americans are at an all time low. The growth in wealth of the Top 1% is at an all-time high, increasing exponentially over the last 30 years, while everyone's income has risen linearly.
In short, there should be concern with what the numbers are telling us, but for exactly the opposite reasons you suggest.