The high unemployment rate - a nagging problem of the current crisis in the United States and Western Europe - seems to be hard to solve, though it is pretty easy to see what has happened. Many jobs have migrated to China and other lower-wage countries in Asia.

But jobs started disappearing long before Foxconn assembly lines in Shenzhen started turning out iPhones, or Korean factories assembled flat-screen televisions. In fact, many tasks once performed by various clerks, agents, secretaries and cashiers are now taken care of by people who already have jobs.

This so-called "shadow work," the phrase coined by the Austrian philosopher Ivan Illich in 1981, takes into account all the unpaid labor that takes place in a wage-based society, Craig Lambert recently wrote in The Times. The technology that lets us pay credit card bills online or scan our own groceries also turns us into employees, eliminating jobs and driving up the unemployment rate.

"Airports now have self-service check-in kiosks that allow travelers to perform the jobs of ticket agents," Mr. Lambert wrote. "Travel agents once unearthed, perused and compared fares, deals and hotel rates. Shadow-working travelers now do all of this themselves."

The march of technology is quickening, according to Erik Brynjolfsson and Andrew P. McAfee, researchers at the Massachusetts Institute of Technology's Center for Digital Business and the authors of "The Race Against the Machine."

"Faster, cheaper computers and clever software are giving machines capabilities that were once thought to be distinctively human, like understanding speech, translating from one language to another and recognizing patterns," The Times reported. "So automation is rapidly moving beyond factories to jobs in call centers, marketing and sales - parts of the services sector, which provides most jobs in the economy."

But masters of the Internet are not likely to go hungry.

These days, "Yield Optimization Manager" and "Director of Platform Marketing" are jobs in high demand, The Times reported. These positions require hard-core quantitative, mathematical and technical skills to analyze Web data for advertising agencies and marketers that want to direct ads to consumers.

"The number of things that you need to know is high," Joe Zawadzki, the chief executive of MediaMath, an ad tech company in New York, told The Times, "and the number of people that have grown up knowing it is low."

Mr. Zawadzki told The Times that it takes two to three months to find the right person for many positions, and those who can write code, create digital ads, develop Web sites and analyze statistics are in high demand, often fetching annual salaries that can reach $100,000.

But even technology workers do plenty of shadow work once taken care of by support staff: writing e-mails, booking flights, making copies and fetching coffee. And all this extra work is wearing down workers. In a 2007 study, 38 percent of Americans said they were fatigued.

"Various mundane jobs were once spread around among us, and performing such small services for one another was even an aspect of civility," Mr. Lambert wrote.

"Those days are over. The robots are in charge now, pushing a thousand routine tasks onto each of our backs."