The first thing I wondered is whether or not this is even remotely true. Do 51% of Americans really pay no taxes? Well, yes and no. While it is true that 51% don't pay any income taxes, it's not true that they don't pay any taxes at all. It also turns out that the reason most of these people don't pay income taxes is because they have no income (like students and seniors) or they're so poor they simply don't make enough money to be taxed. Young people will pay taxes and older people already have so it seems a bit disingenuous to discount them so readily, but to be fair the 51% number is accurate. Then again, call me a bleeding heart but I have a hard time being angry that people who make less than $9,500 a year aren't paying more income tax. This 51% number is also higher because of the recession. According the Center on Budget and Policy Priorities, 35% to 40% is more usual.
Institute on Taxation and Economic Policy broke down the difference really well:
Knowing this, it made me wonder who pays the most taxes overall. Not that it ultimately matters, but you often hear Republicans say the rich carry most of the burden and I wanted to know if this was accurate. It turns out the federal income tax and the payroll taxes both account for about 40% of federal revenues. From 9 Things The Rich Don't Want You To Know About Taxes:
The Internet is awash with statements that the top 1 percent pays, depending on the year, 38 percent or more than 40 percent of taxes. It’s true that the top 1 percent of wage earners paid 38 percent of the federal income taxes in 2008 (the most recent year for which data is available). But people forget that the income tax is less than half of federal taxes and only one-fifth of taxes at all levels of government.So yes 51% of the country may not pay any federal income tax, but the claim is still pretty inaccurate. When all taxes are taken into account (federal, state, and local) even the "poorest fifth of households paid 16.3 percent of their incomes in taxes, on average, in 2010." Admittedly, about 14% of Americans pay neither the federal income tax or payroll taxes but that's nowhere near the often repeated 51% (and those people do pay sales tax and some pay property taxes).
Social Security, Medicare and unemployment insurance taxes (known as payroll taxes) are paid mostly by the bottom 90 percent of wage earners. That’s because, once you reach $106,800 of income, you pay no more for Social Security, though the much smaller Medicare tax applies to all wages. Warren Buffett pays the exact same amount of Social Security taxes as someone who earns $106,800.
If you'd like more information, I found a great breakdown here (pdf): Who Pays? A Distributional Analysis of the Tax Systems in All 50 States