Short answer. The employee. Long answer, let’s check with Walter Williams for that:
A congressional hoax that’s flourished for seven decades is the Social Security hoax that half of the Social Security tax (6.2 percent) is paid by employers, the other half (6.2 percent) paid by employees. The law says that if you are self-employed, you get to pay both halves. The fact of the matter is whether you’re self-employed or not, you pay both halves of the Social Security tax that totals 12.4 percent. Let’s look at it.
Suppose you hire me and our agreed-upon weekly salary is $500. From that $500, you’re going to deduct $31 as my share of the Social Security tax and you’re going to add $31 as the so-called employer’s share, sending a total of $62 to the IRS. Here’s the question: What is the weekly cost for you to hire me? I hope you answered $531.
Exactly. Have you ever wondered where all of the benefits came from (other than from the employer)? Mr. Williams has the answer for that also:
During WWII, Congress imposed wage and price controls making it illegal for companies to compete for employees by offering higher wages. That’s when we saw many companies start to offer nonwage benefits, such as health insurance, as a means of competing for employees.
Amazing. The whole system of benefits was created by businesses who were hampered by government regulation from paying people what the market believed they were worth. One could say that the government caused the two-tier (wage and non-wage) system of remuneration by its interference in the market. Now, modern bureaucrats wish us to think that because the employer pays something to the government directly, it comes at no cost to the employee.
If you simply do the math, you’ll understand the fallacy in that one. Go read the entire article.