Brianna Roy-Rankin, 23, is just the kind of worker Target would like to retain and promote. She says she loved her job at the retailer's store in Champaign, Illinois. She had great bosses, got along well with her co-workers and enjoyed the employee discounts. But last week, after two years as a sales associate, Roy-Rankin quit her job.

“I couldn’t really plan. I was at the mercy of the scheduling system,” she says. “Otherwise, I honestly, probably, would’ve stayed.”

Roy-Rankin went to college nearby, at the University of Illinois. Before she graduated in May, she says it was a constant challenge to balance her studies and social life with her part-time job -- usually around 20 hours a week at just under $10 an hour.

Target has an unforgiving scheduling system. Roy-Rankin says she would have to submit requests to take time off for spring break or visit her parents weeks, if not months in advance -- otherwise she’d be slotted to work without recourse. She would learn about her weekly work schedule three weeks in advance, which wasn’t too bad. But then her hours would fluctuate drastically. One week, she’d be scheduled for a 8 a.m.-to-noon shift on a particular day; the next, it might be a 5 p.m.-to-11 p.m. closing shift. Eventually, it became too much to juggle.

Roy-Rankin's situation is hardly unique.

A Common Trend

Nearly three in 10 hourly workers in the United States say they rarely get consistent work schedules, according to a study released Tuesday by WorkJam, a firm that specializes in workforce scheduling technology.

What’s more, an astounding 56 percent say they get their schedules a week or less in advance. Both trends run rampant in the fast-growing service sector, especially in low-wage fields like retail and fast food. And while policies of this sort save companies money by allowing them to tailor schedules to an expected flow of customer traffic, workers say it's the source of headaches.

Joshua Ostrega, chief operating officer and co-founder of WorkJam, admits the 56 percent figure came as a bit of a shock. “I think it’s extremely high,” he says. “We were actually quite surprised.”

An especially harsh practice among retailers is what’s known as just-in-time or on-call scheduling. Under this system, workers are required to be “on call” to come in and work on a particular day even if they’re not scheduled to do so.

The industry’s profit margins are tight, says Ostrega, and companies are looking to extract savings however they can. Software-based scheduling systems do the trick by linking labor supply to consumer demand. When store traffic is low, the system calls for fewer employees; when the system projects more patrons, it demands more workers. Employers like it because it keeps them from racking up unnecessary labor costs.

Now, unpredictable scheduling is increasingly drawing the interest of public authorities.

'The Pressure's Mounting'

In April, New York Attorney General Eric Schneiderman sent letters to major retailers that inquired about their on-call scheduling and asked whether their policies violated state law. Like seven other states and the District of Columbia, New York has so-called reporting-time laws that require employees to be paid when they report to work, even if no work is provided.

Since the letters went out, a number of high-profile companies have announced changes to their policies. The Gap and Abercrombie & Fitch, which both received the notices, said they would end the practice of on-call scheduling. And Starbucks promised last year to provide more consistent scheduling to baristas. But as a recent story in the New York Times revealed, the cafe chain has failed to do so.

Robert Hiltonsmith, senior policy analyst at Demos, a progressive think tank, expects the positive trends to continue -- even if Tuesday’s survey suggests employers overall aren’t relenting on tough and irregular scheduling demands. “I think it’s a slow burn, but the pressure’s mounting,” he says.

It’s in part a question of economic self-interest, Hiltonsmith says. Burned-out workers tend to quit their jobs fairly quickly, and high turnover is expensive. That’s one of the reasons why Walmart, the nation’s largest private-sector employer, and its top competitors voluntarily hiked wages earlier this year, according to Hiltonsmith. In fact, when Walmart announced it was boosting starting pay to at least $9 an hour, it also promised to notify workers of their schedules at least two and a half weeks in advance.

Reforms like this and others -- shifts that are scheduled the same time every week -- could prevent retailers from losing employees like Roy-Rankin, the kind of people who are otherwise content at work.

There’s also mounting political pressure, which stems from growing public concern over the livelihood of service-sector workers. Hiltonsmith attributes this to the “seismic shifts in the labor force” -- the decades-long decline of manufacturing and growth in service-sector employment.

Contrary to the popular image, retail workers are not teenagers looking to make a quick buck. The median age of a retail trade employee is 38, according to the federal Bureau of Labor Statistics.

“I think people had less concern when it wasn’t people trying to support their families,” Hiltonsmith says. “For better or worse, the service economy is the economy of the country’s future.”