Establishing a secure retirement for American workers is a social good, too. And the United States already has one type of public option—Social Security—designed with that purpose in mind. The venerable program offers a baseline public pension to Americans. No one is required to take it, and anyone can add private savings or a private pension on top of it.

While expanding Social Security would be a big help for many retirees, Social Security was never intended to fully fund anyone’s retirement. The average new retiree collects benefits of about $1,470 a month, or $18,000 a year. That’s a welcome safety net, but economists estimate that most people need about 60 percent of their pre-retirement income to maintain their living standard. Employer pensions and private savings are supposed to make up the difference.

Joshua Gotbaum: The federal government gave up on retirement security

But over the past few decades, employers have shifted the financial risks of retirement onto workers. The first problem is that, between the decline of unions and the hunger for higher corporate profits, more than half of American workers now have no workplace pension of any kind. Those who are lucky enough to have a retirement plan at work face a second problem. The vast majority of plans now are defined-contribution plans, such as 401(k)s, rather than defined-benefit plans. This means that workers can’t count on a fixed sum of money every year in retirement (the defined benefit). Instead, they put aside a fixed sum while working (the defined contribution) and are left to the whims of the stock market for their retirement savings. A few bad investments or a stock-market crash at the wrong moment can mean calamity.

The third problem is that investing isn’t just complicated; it can be dangerous. Some products have high fees that can erase investment gains, and many investment advisers have no legal obligation to act in the best interest of their clients. Some even receive bonuses and kickbacks from investment funds. The fourth problem is the bittersweet risk of simply outliving your savings.

The reality is that the combination of Social Security and private retirement products hasn’t been sufficient to guarantee all Americans—or even a majority of Americans—an adequate standard of living in their later years. Congress should shore up Social Security. But American workers need something more.

Here’s how the public option that we propose would work: Every American would automatically be enrolled in a retirement program that would withhold, say, 3 percent or 5 percent from every worker’s paycheck. The money would be deposited in a retirement savings account managed by the federal government, and the savings would be locked up until retirement. Savers would have limited investment choices, and the short menu would include only low-fee index funds, such as a “life cycle” fund targeted to the saver’s intended retirement date. At retirement, the balance would be converted to a life annuity, paying a guaranteed sum every month for the rest of the worker’s life. No one would be required to participate, and market options would compete side by side with this public program.