I found an interesting summary of the Joint Economic Committee Study titled Payroll Taxes and the Redistribution of Income. It's an interesting read, particularly since it notes that even under the current system, a $50,000 per year wage earner would get more out of simply saving the money that goes into Social Security than what is paid out at retirement. The break-even point appears to be somewhere around $20,000-$25,000, with anything above that being used to fuel payments to those that didn't make that much throughout their careers.