Depends on the pay scale of the retiree during their working years. Lower income people get a really good return, with the really low $ workers getting a huge risk-free windfall.
Those at the high end get effectively less than 0%, meaning they could have put it into long-term Treasury bonds and made 2%+, but instead will get a negative return.
Consider, too, that the tax rate went up in the early 80s, so older retirees are doing EVEN BETTER than this if they were at the lower income scale.
For a few years only part of my income was charged SS tax because I was over the maximum. But they substantially increased the maximum taxable so that ended pretty quickly.
The good news is that your SS payments are based on what you put in, at least to a degree.