When an employer considers hiring you or raising your pay, he balances the benefit of your future servicesto his business against the total cost to his business of paying you. He does not decide what to pay you and then get flummoxed to learn that he has to pay as much Social Security "payroll tax" as you do; what kind of employer is naif enough not to already know that??!
So in essence you pay the "employer's contribution" as well as your own. Thus, Social Security tax is way over 10%--which if prudently saved and invested would be quite ample for a comfortable retirement. But of course the money is not saved--it is by law "invested" in claims on future general fund revenues, a.k.a. "risk-free government bonds." Which simply means that the government spends the money as fast as it comes in, if not more so--and if it did not spend the money, the result would be deflation.
Clearly then, if there is to be a real Social Security Trust Fund which actually prevents poverty and does not cause a macro economic meltdown, it must be invested in the private economy. But if the government invests that kind of money in the private economy, it will quickly acquire a huge stake in our major corporations--and the Democrats will put politicians on the boards of directors thereof. IOW, socialism.
The conclusion is that the SSTF must be invested in the real economy rather than in government bonds, but that investment must be controlled by the taxpayer individually rather than by the government.