But unions, a powerful force in improving wages and social welfare programs in the West in the 20th century, are struggling in the 21st. Their members now compete with cheap labor in emerging economies and with ever smarter, faster and cheaper machines. With the exception of the Nordic countries, union membership in most rich industrialized nations has plummeted, to 17 percent across the member countries of the Organization of Economic Cooperation and Development.

Might inequality become a rallying cry? Many experts are skeptical.

“An increasingly globalized and technology-intensive system can’t be counted on to bargain on behalf of labor” in Western countries, said Stephen Roach, a Yale economics professor and a former chairman of Morgan Stanley Asia.

Indeed, at a time when not just the number of unionized workers but work itself may be getting scarcer, unions need to change as radically as the economy around them, said Andrew McAfee, a professor at the Massachusetts Institute of Technology.

“All the old assumptions would have to go,” said Mr. McAfee, co-author of “The Second Machine Age,” a soon-to-be published book about technology’s effect on employment. He will be attending Davos this week for the first time.

In coming years, he predicts, machines will be able to do many of today’s jobs, whether as driverless taxis, buses and delivery vans, or as lettuce-picking robots. Long term, the only way to keep people employed and socially mobile is to create an education system that produces digital-age workers whose skills are complementary to machine intelligence, Mr. McAfee said.

Meanwhile, governments need to be open to new — and sometimes old — ideas of redistribution, he said. Maybe most important, he said, is an overhaul of a taxation system that in most countries still overwhelmingly relies on revenue from labor sources like income and payroll tax. “There is a very simple rule of economics,” Mr. McAfee said. “If you want less of something, tax it. If you want more of something, subsidize it.”

The Rover factory where Mr. Jennings’s father worked was closed long ago. A supermarket opened in its place.