Why does that count employee social security contributions, but not employer contributions? Both ultimately come out of your paycheck. The fact that social security contributions are split is just a fiction that makes the tax rate look lower.
It also sounds like it doesn't count state and local income taxes, nor property taxes or any of the many other taxes we have the privilege of paying.
The conclusion may well be correct, but the data presented doesn't seem to be nearly complete enough to support it.
It's specifically a cost of labor. The business spends $X on you as an employee, and you receive $Y. The difference between X and Y is tax. The fact that some of the difference is technically removed before the money is transferred to you, and some of it is technically removed after the money is transferred, makes no difference in the end.
I think the "fundamental difference" is key. I don't ultimately see any real difference between taking 12.4% of my pay (under $118,500) for Social Security, and taking a variable percentage of my pay for government operations in general. It's money, based on a percentage of what I earn, that goes to the government, i.e. an income tax.
It also sounds like it doesn't count state and local income taxes, nor property taxes or any of the many other taxes we have the privilege of paying.
The conclusion may well be correct, but the data presented doesn't seem to be nearly complete enough to support it.