Use a self-checkout lane at the supermarket or drugstore? A worker behind a cash register used to do that.Buy clothes without visiting a store? You've taken work from a salesman. Click "accept" in an email invitation to attend a meeting? You've pushed an office assistant closer to unemployment. Book your vacation using an online program? You've helped lay off a travel agent. Perhaps at American Express Co., which announced this month that it plans to cut 5,400 jobs, mainly in its travel business, as more of its customers shift to online portals to plan trips. Software is picking out worrisome blots in medical scans, running trains without conductors, driving cars without drivers, spotting profits in stocks trades in milliseconds, analyzing Twitter traffic to tell where to sell certain snacks, sifting through documents for evidence in court cases, recording power usage beamed from digital utility meters at millions of homes, and sorting returned library books. Technology gives rise to "cheaper products and cool services," says David Autor, an economist at MIT, one of the first to document tech's role in cutting jobs. "But if you lose your job, that is slim compensation." Even the most commonplace technologies â¿¿ take, say, email â¿¿ are making it tough for workers to get jobs, including ones with MBAs, like Roshanne Redmond, a former project manager at a commercial real estate developer. "I used to get on the phone, talk to a secretary and coordinate calendars," Redmond says. "Now, things are done by computer." Technology is used by companies to run leaner and smarter in good times and bad, but never more than in bad. In a recession, sales fall and companies cut jobs to save money. Then they turn to technology to do tasks people used to do. And that's when it hits them: They realize they don't have to re-hire the humans when business improves, or at least not as many.