What's really going to bake your noodle is a concept called "maximum taxable earnings." If you make up to $118,500 a year, you pay 7.6% of your earnings to social security. If you make 118,600 a year, you pay 7.6% of 118,500. If you make $118,500,000.00 a year, you pay 7.6% of $118,500.00. When you hear about social security going bankrupt? Yeah, pretty easy fix.
Check out our USC http://www.citizensinformation.ie/en/money_and_tax/tax/income_tax/universal_social_charge.html Which is 8% of your gross salary if you earn 100K before they take the other 21/42% PAYE tax. Essentially half your salary goes to tax... It makes for interesting conversations when my US based co-workers make the occasional gripe about salary or cost of living, my heart bleeds for them.