Is Labor Day slouching toward irrelevance? Maybe. The value of human labor, as we know it, is declining. The percentage of the nation's economic output paid out in wages stands at the lowest point since the government began keeping track in the 1950s. The nation's most valuable company, Google, is worth an estimated $395 billion but employs only 55,000 people. In 1964, the nation's most valuable company, AT&T, was worth $267 billion in today's dollars but employed nearly 14 times more workers — 760,000.

Globalization explains much of the trend, although, as computers and software continue to take over human jobs, automation may be the bigger factor. In his fascinating piece "A World Without Work," published in last month's issue of the Atlantic, Derek Thompson recalls that for centuries new technologies were devised to expand the value of horses — better plows, deadlier swords and lances, more efficient carts and wagons. Then, in the space of a few decades, horses vanished from the labor force. Are humans now in a similar position?

Not quite. But, as Thompson tells it, technology has begun to exert slow and steady downward pressure on the value and availability of work; eventually, a "new normal" could greatly reduce the expectation of work as a central feature in the adult lives of most Americans. For the moment, a recovering economy and falling unemployment numbers conceal the deeper structural problems with labor. But the next recession will surely bring another wave of cybersubstitutes for full-time workers.

Not so long ago, economists thought it far-fetched that robots might diagnose disease, tend bank accounts, serve fast food or unload ships. But now, if you take seriously the potential for driverless cars, trucks and aerial drones, it's hard to dismiss John Maynard Keynes' 1930s prediction that the economy of the 2030s would require a human workweek of only 15 hours.

Fear of technology is hardly new. Ever since the Luddites smashed weaving machines in the early 1800s, worries about the "end of work" have persisted. But technology seemed always to produce as many jobs as it eliminated. Now that may be changing.

Oxford University researchers predict that technology will be capable of performing nearly half of all U.S. jobs within the next two decades. That's likely to further widen the nation's social and economic gaps and deepen the alienation among rising numbers of prime-age men who don't have jobs and aren't looking for work. In his new and otherwise optimistic book, "The Second Machine Age," MIT's Erik Brynjolfson concedes that many people without creative or social skills will be left behind, without work.

Any transition from labor to leisure might be especially hard on Americans, who work harder and longer than most everyone else in the world and for whom industriousness symbolizes the national character. A decline of work would seriously alter not just the nation's economy but its politics and social order. That prospect has led economists and social thinkers to imagine a new world with less work — or, at least, less of what we now think of as work, the kind that pays wages, supports families and offers a semblance of security.

Some forms of post-wage work are already common. Corporations and governments routinely hire consultants and freelancers for less money to work on projects that were once handled in-house. A new era of arts, crafts and home industries seems also to be emerging. A return to trade and barter systems may not be far behind. Some experts anticipate huge networks of online exchanges that sort out workers for tasks large and small — everything from cutting grass to writing symphonies. There's evidence that autonomy brings added happiness and creativity. Still, it's hard to imagine that post-wage workers will be able to afford the goods and services that they help produce.

Thompson, in his Atlantic piece, retells a story from the 1950s about Henry Ford II showing labor leader Walter Reuther through a mock-up of a futuristic auto factory. Ford asks, "Walter, how are you going to get these robots to pay union dues?" Reuther replies, "Henry, how are you going to get them to buy your cars?"