But even putting income shocks aside, she said, most human beings lack the skill and emotional wherewithal to be good investors. Linking investing and retirement has turned out to be a recipe for disaster.

“People tend to be overconfident about their own abilities,” said Ghilarducci. “They tend to focus on the short term rather than thinking about long-term consequences. And they tend to think that whatever the current trend is will always be the trend. That is why people buy high and sell low.” Financial advisers — at least the good ones — are forever telling their clients to be disciplined, to create a diversified portfolio and to avoid trying to time the market. Sound as that advice is, it’s just not how most humans behave.

That data starkly backs up Ghilarducci’s contention. According to the Employee Benefit Research Institute, for instance, only 22 percent of workers 55 or older have more than $250,000 put away for retirement. Stunningly, 60 percent of workers in that same age bracket have less than $100,000 in a retirement account. Ghilarducci told me that the average savings for someone near retirement in America right now is $100,000. Even buttressed by Social Security, that’s not going to last very long.

What, then, will people do when they retire? I asked Ghilarducci. “Their retirement plan is faith based,” she replied. “They have faith that it will somehow work out.”

I laughed, but it’s not funny. “The 401(k),” she concluded, “is a failed experiment. It is time to rethink it.”

In truth, I’m one of the lucky ones. I do work that I love, which requires no heavy lifting and has no mandatory retirement age. If I become incapacitated, I will have assisted-living insurance. Otherwise, I can keep writing till I drop.

But, for the millions of others who have discovered, as I have, that their original enthusiasm for investing was unwarranted, their faith-based retirement plan is all they’ve got left.