One main selling point that unions use for why workers should join them is the good retirement benefits. In an era of 401ks, which can go up and down with the market, they promised guaranteed pensions, and, for the most part, they used to deliver.

There is, however, a catch that now threatens the retirements of hundreds of thousands of workers. Companies may be on the hook for this catch through no real fault of their own. Unions ought to be as well, though they’d prefer taxpayers foot the bill.