The Rich Should Pay Their Fair Share

How often have we heard that refrain, especially from Democrats in the US? Whenever there is a budget crunch, the answer is to tax the rich more. The health care bill just passed does this, taxing the top 2%. If only the rich paid their fair share, everything would be better, we're told. Canada's NDP loves this refrain as well. The Left would pay for everything by increasing taxes on the rich. After all, it is common knowledge that the rich, the top percentiles, don't pay their fair share of taxes. Of course, like most things that are "common knowledge," this too is wrong.
Look at the income taxes collected in the US for example. As a percentage of all income tax that is brought in, here's who pays what:

So, the top 20% of income earners pay over 83% of all the income taxes collected. That sounds like a fair share to me. After the richest 20% get through paying taxes, the government has only 14% to collect form the remaining 80% of taxpayers. What's more, look at the bottom 40%. These people actually receive more refundable tax credits from government than they pay, so as a whole, they pay no income taxes at all. That's 40% paying on average no income taxes while the top 20% pay the vast majority of all income taxes. The highest earning amongst us should pay more tax than the poor and middle class, but let's not indulge those who suggest that taxing the rich is the obvious and equitable way to raise revenue.