This column is getting wrapped up at about my 50th hour of work in what's traditionally considered the first week of summer, when the kids get out of school.

It was my idea to work that long, writing another column instead of winding down for a long-planned week off, just because a topic seemed too interesting to pass up. And 50 hours of work isn't even a particularly long workweek for a lot of Americans.

It wasn't supposed to be like that by now, of course, and such long weeks would sure be surprising to the economist John Maynard Keynes. He once famously predicted that the average workweek should have shrunk to maybe 15 hours by now.

This might be the most discussed thing Keynes ever wrote, in a short 1930 essay that looked ahead 100 years to the economic lives of his grandchildren.

He turned out to be mostly right that using technology to boost productivity would lead to huge gains in our material wealth. He would be puzzled to know why we didn't choose to use our great material wealth to work any less.

The answer, of course, is that for a lot of us, hard work isn't really an economic decision.

His prediction of three-hour shifts seems almost comically naive to us, but all he did was forecast off the trends he could see. When he was young, the average workweek in America was more than 60 hours and no one talked about family vacations.

He was right for a while, too, as the average workweek declined from about 47 hours at the time his essay was written to not quite 39 hours by 1970. That's about when the average workweek stopped getting shorter.

That's the average, and since 1970, there has been a growing divide in hours worked based on what kind of work Americans do. Between 1979 and 2002, the frequency of working 50 hours or more in a week increased by 14.4 percentage points among the top 20 percent of wage earners, typically college-educated managers and professionals, but it actually slipped by nearly 7 percentage points for the lowest-paid workers.

That divergence in the workweek is reflected in the economic anxiety of hourly workers, as shown in a poll last year by Marketplace. About half of them said they preferred more hours at work, not less.

For white-collar professional jobs, on the other hand, hours worked have been rising for years. The top complaints may be over work-life balance or unplugging from round-the-clock e-mail.

Just why well-paid professionals and managers are working so hard is a bit of a puzzle. For a married couple with two great salaried positions, they seem to be blessed with both enough income to pay for nice things and the opportunity to cut back at work.

Based on watching young families, it's far more likely that the couple both work 50 or more hours a week, hiring people to clean the house and take care of their kids.

One explanation for why managers and professionals are working so hard is that they found themselves on the hedonic treadmill, a well-known principle in behavioral economics that basically means people quickly adapt to having nice, new things.

They grew accustomed to a new luxury car, the relaxing winter vacations in the sun and a big house. They worked even longer hours to make sure the best jobs or clients or projects didn't go to someone else, putting their affluent lifestyles at risk.

That's not an explanation that convinces the Harvard economist Benjamin Friedman, author of a fascinating recent paper about Keynes' essay.

Friedman found a better explanation in how median family income, adjusted for inflation, seemed to stop growing at about the time the workweek stopped getting shorter. That is, the increasing productivity did not seem to be broadly shared in better lifestyles.

He also noted that it wasn't that long ago that most Americans did jobs that were genuinely backbreaking, working long days in smelly and dangerous places. That's why in traditional economic thinking, work was something that generated "disutility," meaning our work actually made our lives worse.

It was the money people got paid for their work that bought the nice things that made their lives better.

Now, more than a third of Americans are professionals or managers, Friedman said. They are working long hours because it's the work that is making their lives better, not just what their wages can buy.

It turns out to be very satisfying to work a long week with colleagues to solve hard problems at work. Work is also where our best friends are now found as civic and volunteer organizations, everything from hobbies to church congregations, fade in importance to our lives.

Ryan Avent, an economics writer and editor for the Economist, wrote this year that those factors help explain why he has an all-consuming career that his own parents can't seem to understand. They remain curious why he chooses long hours in London rather than working closer to where he grew up in North Carolina.

"They are asking about a job," he wrote. "I am thinking about identity, community, purpose — the things that provide meaning and motivation. I am talking about my life."

In my own circle of friends, now that the kids are mostly out of high school, we talk more about our own futures and the coming end of our careers. Even now, in our mid-50s, retirement from our time-consuming daily jobs remains mostly an abstraction

The best explanation for why retirement seems so far off is that our work continues to be by far the most interesting way to spend a day.

One friend, an engineering project manager, has a new job and many new engineering problems to occupy his thinking. Another may still be paying off the loans from her latest graduate school degree and still talks like she's closer to the start of her career than the end.

This kind of thinking about the non-monetary rewards from work even colors the advice I get from my own financial adviser, Craig Shaver of RBC Wealth Management.

Just before the Memorial Day weekend, I asked for a meeting with him. He promised not to bring another three-ring binder, making this more a beer after work with a friend.

I just wanted to hear that we had saved enough to retire whenever we wanted. Shaver answered with just one word, but for him this conversation about retirement was just getting started.

"As your sometime adviser, I've just got to ask," he said. "Why would you want to?"

lee.schafer@startribune.com • 612-673-4302