The front-page headline in a recent Washington Post was breathless: “These companies say AI is key to their four-day workweeks.” The subhead was euphoric: “Some companies are giving workers back more time as artificial intelligence takes over more tasks.”

As the Post explained: “more companies may move toward a shortened workweek, several executives and researchers predict, as workers, especially those in younger generations, continue to push for better work-life balance.”

Hurray! There’s utopia at the end of the AI rainbow! A better work-life balance!

You may have come across similar articles in Fortune magazine and the New York Times. The AI spin brigade is in full force.

Business leaders are rhapsodizing about how AI will free their employees to take more time off. Zoom’s Eric Yuan told the Times that “A.I. can make all of our lives better, why do we need to work for five days a week? Every company will support three days, four days a week. I think this ultimately frees up everyone’s time.”

Jamie Dimon, CEO of JPMorgan Chase, says advancing technology could push the workweek down to just three and a half days. The Microsoft co-founder Bill Gates openly wonders whether a two-day workweek could be the future.

Elon Musk pushes the idea to the extreme (as he does everything else): “In less than 20 years – but maybe even as little as 10 or 15 years – the advancements in AI and robotics will bring us to the point where working is optional.” Even better: “There will be no poverty in the future and so no need to save money,” says Musk. “There will be universal high income.”

All of this is pure rubbish. Even if AI produces big productivity gains – which is still an open question (an MIT study last year found that “despite $30–40 billion in enterprise investment into GenAI, 95% of organizations are getting zero return”) – it’s far from clear that workers will see much, if any, of the benefits.

If productivity rises, as it’s supposed to do when the workplace becomes immersed in AI, each worker will generate more value, by definition. And supposedly with more value, we’re all better off.

Worker productivity has been rising for years, yet the median wage has barely risen, when adjusted for inflation.

Here’s the truth: the four-day workweek will most likely come with four days’ worth of pay. The three-day workweek, with three days’ worth. And so on.

So, as AI takes over their current work, most workers will probably get poorer or have to take additional jobs to maintain their current pay.

In his 1930 essay Economic Possibilities for Our Grandchildren, the great British economist John Maynard Keynes predicted that in a century, “the discovery of means of economizing the use of labour” would outpace our ability to “find new uses for labor”. In other words, less work.

Keynes was sure that by 2030 the “standard of life” in Europe and the United States would be so improved by technology that no one would worry about making money. Productivity gains would create an age of abundance.

In fact, by 2030, he predicted, our biggest problem would be how to use all our leisure time:

“For the first time since his creation man will be faced with his real, his permanent problem – how to use his freedom from pressing economic cares, how to occupy the leisure, which science and compound interest will have won for him, to live wisely and agreeably and well.”

We’re still five years away from Keynes’s magic year, but at the rate we’re going, his prediction seems wildly wrong.

Rather than creating an age of abundance in which most people no longer have to worry about money, new technologies have contributed to a two-tiered society comprising a few with extraordinary wealth and a vast number of people barely making it.

AI is likely to further widen inequality.

Imagine a small box – call it an iEverything – capable of producing for you everything you could possibly desire. It’s a modern-day Aladdin’s lamp. You simply tell it what you want and – presto! –the item or service suddenly appears.

Sounds wonderful until you realize that no one will be able to buy the iEverything because no one will have any means of earning money, since the iEverything will do everything.

This is obviously fanciful, but the dilemma is very real. Productivity gains are great, but the too-little-discussed question is how they will be distributed.

The distribution issue can’t be ignored. When more can be done by fewer people, who gets paid what? It comes down to who has the power.

Unless workers have the power to demand a share in the productivity gains, profits will go to an ever-smaller circle of owners – leaving the rest of us with less money to buy what can be produced.

If the five-day workweek with five days of pay shrinks to four days with four days of pay, and then to three, and to two, and perhaps one, AI will supplant most people’s work and drive down our take-home pay. We may see a dazzling array of products and services spawned by AI, but few of us will be able to buy them.

But this isn’t necessarily our fate. If AI does deliver big productivity gains, how can average working people get a share of those gains? They can get a share if they have the bargaining power to get it.

It seems doubtful that labor unions will provide that power. Forty years ago, over a third of the private-sector workforce was unionized. Now, it’s only 6% – not much power there.

Which leaves politics. Will average working people gain the political muscle to demand a share of AI’s productivity gains?

That depends on whether one of our two dominant political parties will demand and enact laws that distribute those gains more fairly (think wealth taxes financing childcare, elder care, and healthcare, for example).

If not, maybe a third party emerges – a workers’ party – dedicated to this?

In the meantime, don’t fall for the breathless rubbish about AI allowing employers to “free up” employees’ time.

The real question is whether AI’s productivity gains, if it delivers, are shared with workers. And the truth is employers won’t share those gains unless they’re forced to.

• Robert Reich, a former US secretary of labor, is a professor of public policy emeritus at the University of California, Berkeley. He is a Guardian US columnist and his newsletter is at robertreich.substack.com. His new book, Coming Up Short: A Memoir of My America, is out now