This is a question regarding the social insurance tax in the U.S.
The effective payroll tax cited by the Congressional Budget Office as well as the Tax Policy Center is lower than I would expect for a middle class American.
As I understand it, the tax rate is 6.2% for Social Security and 1.45% for Medicare. The employer has to match this so the total tax is 15.3%. (With self-employed workers paying the entire amount themselves.)
However if you look at the tables in the links below, you can see the effective social insurance tax never hits even 11%. Both the CBO and the TPC include the employer contribution (otherwise the number should never go above 6.2% + 1.45% = 7.65% either).
What's going on? As I understand it, the standard deduction and so forth does not apply. The payroll taxes apply directly to your gross income, not adjusted gross income, so I would think the effective tax is 15.3% for those earning less than the Social Security Wage Base ($113,700 in 2013.)
"Although both employees and employers pay FICA taxes, most economists believe that the employer’s share is fully offset by reduced wages and thus the entire economic burden of the tax ultimately falls on workers."