Social Security is 7% starting with the FIRST DOLLAR EARNED. Your Employer Matches that 7% (Total of 14%). Every economist will tell you that the employer match is really a tax on the employee's income and should be treated as such.
Second you have your 2.1% Unemployment tax which like Social Security starts with your first dollar earned AND is paid by your employer but most economist consider this a tax on the Employee not the employer.
Thus before you ever talk about local taxes, state taxes and the Federal Income Tax you have people paying 7% of their income to Social Security and having their employer pay another 9.1% of their income as taxes. While technically you are only paying 7% of your income in taxes, the Federal Government is collecting as taxes an amount equal to 16.1% of your income.
If you have a local Wage tax (Such as in my home state of Pennsylvania) you paying 2% from the first dollar earned. The same with the Pennsylvania Income tax, which also starts at the first dollar and is a flat rate of 3.07%.
Thus in Pennsylvania any employee pays combined Social Security, Local and State Income tax rate from the first dollar earned of 12.07%. The taxes collected based on his or her income is 21.07% (Remember the Social Security employer match AND the Unemployment tax both paid by the employer BUT based on the employee's income).
In other states this will vary based on the State Income tax and the local wage tax.
For list of State Tax Rates see:
For Income Taxes see:
http://www.taxadmin.org/fta/rate/ind_inc.html For Sales Taxes see:
http://www.taxadmin.org/fta/rate/sales.html