But recent advances—everything from driverless cars to computers that can read human facial expressions—have pushed experts like Mr. Brynjolfsson to look anew at the changes automation will bring to the labor force as robots wiggle their way into higher reaches of the workplace.

They wonder if automation technology is near a tipping point, when machines finally master traits that have kept human workers irreplaceable.

“It’s gotten easier to substitute machines for many kinds of labor. We should be able to have a lot more wealth with less labor,” Mr. Brynjolfsson said. “But it could happen that there are people who want to work but can’t.”

In the Australian Outback, for example, mining giant Rio Tinto uses self-driving trucks and drills that need no human operators at iron ore mines. Automated trains will soon carry the ore to a port 300 miles away.

The Port of Los Angeles is installing equipment that could cut in half the number of longshoremen needed in a workplace already highly automated.

Computers do legal research, write stock reports and news stories, as well as translate conversations; at car dealers, they generate online advertising; and, at banks, they churn out government-required documents to flag potential money laundering—all jobs done by human workers a short time ago.

Microsoft co-founder Bill Gates , speaking in Washington last year, said automation threatens all manner of workers, from drivers to waiters to nurses. “I don’t think people have that in their mental model,” he said.

Gartner Inc., the technology research firm, has predicted a third of all jobs will be lost to automation within a decade. And within two decades, economists at Oxford University forecast nearly half of the current jobs will be performed with machine technology.

David Fuller's view

This is progress.  Rapidly developing robotic machines are wonderful and any time humans are replaced by machines, productivity increases.  The biggest beneficiaries are the increasingly automated companies.  The next biggest beneficiaries are shareholders who invest in these firms.

The biggest losers are people who find themselves out of work, for no fault of their own, because they have been replaced by machines which can work around the clock, seven days a week if required.  The second biggest losers are governments which find that they are collecting fewer and smaller payroll taxes, and are also having to subsidise the unemployed. 

Luddite, anti-robotics demonstrations are pointless.  There is no turning back the clock on progress.  Instead, individuals, families, schools and universities, job counsellors and governments need to think creatively about new jobs which will still require people.  They will, but I have long said that the accelerating rate of technological innovation ensures that jobs are being replaced more rapidly than they can be created at present.     

(See also Eoin’s comments below on this subject.)