Oh, holiday shopping. It recalls the bombing of Dresden. The jumbled stores look like they've been blitzed, and the sales clerks appear shell-shocked. At some shops, the experience is about as merry as a combat tour, except there's jingly music blaring, and you're not wearing a helmet.

The chaos is due to the fact that at many stores, there just aren't enough trained elves on hand to run the registers and refold the sweaters -- and the situation won't be much better this year. While holiday sales are expected to climb, consulting firm Hay Group says, most shops will maintain last year's staffing levels. This could backfire. According to one survey, 28 percent of store visits last Christmas ended with a shopper ditching her purchase because she couldn't find anyone to help her or because the lines were too long. Other surveys say bad service is driving folks to shop online.

Stores aren't oblivious to the problem, of course, and they put far more effort into staff scheduling than you'd ever imagine. Rather than leave the task up to local store managers, for example, the Bon-Ton department store chain employs a squad of scheduling experts at its York, Pa., headquarters. The team works weeks in advance to come up with hour-by-hour staffing plans for all 275 stores, down to the departmental level. COO Barbara Schrantz says the team uses software to forecast hourly sales for each department and suggest a labor budget intended to maximize sales and profits. There's even a different staff-to-sales formula for each department. Jewelry and shoes get more clerks for every, say, $10,000 in projected sales than housewares would.

The detail can be dizzying. Many stores plan schedules in 15-minute increments -- if sales are expected to pick up at 12:15 p.m., the retailer will put an extra person on the floor. Some even factor in the productivity of individual clerks, scheduling their best salespeople at peak hours.

If the computers have it all figured out, why do we still experience holiday madness? One problem, says Marcelo Olivares, an operations professor at Columbia Business School, is that it's hard to tell when you've stretched clerks to the point where you're losing sales. Customer surveys are notoriously biased (since demanding customers are too busy to take them), and mystery shoppers are expensive. But ask any drudge at the register this season and they'll tell you the truth: "Optimized" scheduling can be rough on employees. It can have them working odd shifts at a frantic pace or juggling jobs at multiple retailers in an effort to assemble a 40-hour workweek. No wonder they're cranky.

Plus, when a store is looking to boost earnings, there's a huge temptation to trim the sales force. This can trigger a death spiral, says Nikki Baird, a partner at Retail Systems Research. When service gets really bad, sales take a dive, and the store responds with more cuts. Pretty soon, the retailer's left with no staff -- and zero revenue. Hello, Circuit City!

The industry's response to this conundrum is, of course, more technology. Workforce-management outfit Kronos says some clients rely on its productivity meter, which flashes into the red zone when sales exceed worker capacity. Others use smartphone apps to page workers when they're needed at the store. If things actually improve at the mall, let me know. Meanwhile, I'll be home, shopping online.