As we head into the holiday weekend, many of us know with certainty what days and hours we’ll be working over the coming week. We’ll enjoy September 7 in honor of Labor Day and then return to our offices first thing Tuesday morning to begin a shortened workweek.

A significant share of the workforce, however, isn’t quite so fortunate. Millions of employees awake every morning without knowing what time they’ll start work, how long their shift will last or even if they’ll be working at all, regardless of what the company schedule says.

Whether it will truly be a “labor day,” and compensated accordingly, remains up in the air for these workers until they get a call confirming that they need to come in to work and for how long.

This type of on-call scheduling has always been a component of certain occupations, such as doctors, firefighters and substitute teachers, a risk compensated for in their salaries. But in recent years this practice has spread to jobs like retail sales work, among the fastest-growing occupations and for which there is little or no extra compensation.

The growing frequency of employees being required to be “on call” during the day or sent home early before their scheduled shift ends became an issue of public concern in April, when New York’s attorney general asked 13 retailers in the state about their scheduling practices, requesting that show they are in compliance with its laws.

Perhaps that’s what prompted Abercrombie & Fitch, Victoria’s Secret and Gap to announce plans to soon end the practice of on-call scheduling. But the battle won’t be over until far fewer workers are exposed to the hazards of irregular work schedules and shifts that do not reflect their choice.

So why should we care how employers schedule their employees’ work? First, let’s look at how on-call scheduling works and who’s affected.

Always On Call

The practice stems in part from employers that have adopted sophisticated software allowing them to predict with greater precision how many shoppers will be in the store at a given time. Thus, they can minimize daily labor cost by monitoring in real time whether they need more employees, calling them in as needed with less than 24 hours’ notice.

This at least sometimes entails not being called in at all or being sent home upon arrival, soon after a shift starts or before the shift even begins without pay for the initially scheduled hours.

In New York and seven other states and Washington, DC, the law requires that employees be paid for a minimum of two to four hours of work – known as “minimum reporting pay” – if their shift ends earlier than planned or is outright canceled. Other states have no laws regulating the practice, although several have adopted proposals to require more advanced notice for scheduling or pay requirements for last minute changes to such schedules, to disincentivize this.

Obviously, this practice creates perpetual uncertainty for these employees, who neither know how much money they’ll make week to week or the times they’ll be free to address their other responsibilities. Many of these employees are trying to coordinate work with caregiving and/or schooling commitments, which are sectors not typically accommodating to sudden changes in a parent’s or student’s work schedule.

By contributing to income instability, this variability of work hours also adversely affects household consumption and the broader general economy, particularly when workers’ hours are restricted.

It is at least partly responsible for the stubbornly high rate of underemployment among workers who prefer full-time employment but had only part-time hours in the previous week.

The On-Call Economy

Recent research findings from the Economic Policy Institute think tank, using General Social Survey (GSS) data up through 2014, provides a snapshot of irregular or on-call shift working:

About 10% of the workforce is assigned to irregular and on-call work shift times, a conservative estimate. Adding to this the 7% of the employed who work split or rotating shifts, about 17% of the workforce have irregular shift schedules.

By income level, the lowest-paid workers (under US$22,500 a year) are more likely to face irregular work schedules.

By occupation type, about 15% of sales and related occupations have such schedules, and they’re most prevalent in the services, hospitality and retail trade industries.

In a recent poll of working adults, conducted by Public Policy Polling for the Employment Insecurity Network at the University of Chicago, as many as 16% reported that their shift time was “irregular.” Another 5% said their shifts were “rotating” and 3% reported working a “split shift,” meaning that about one-quarter of the work force has unstable work scheduling.

The high proportion of workers reporting irregular work schedules is not terribly surprising given that 45% of those in the International Social Survey Program Work Orientations sample (in 2005) said that their “employer decides” their work schedule, while only 15% felt that they were “free to decide” their work schedule. This conforms to more recent findings that just under half of their sample of workers early in their careers said their daily start and end times are decided entirely by their employer, without their input.

More Work-Family Conflicts and Job Stress

So beyond the impact on underemployment and economic recovery, why should we care if a share of Americans are working irregular hours? Because there may be adverse effects on employees who work irregular shift times, compared to those with more standard, regular shift times. This, in turn, might come back to undermine their job performance and thus, their employers’ long-term costs and bottom line.

The frequency with which a worker reports experiencing interference of their work with family time (which might entail, for example, missing children’s performances or games or helping with care) is exacerbated by having irregular shift work times. This association occurs for both hourly and salaried workers, for that latter group even stronger, even after controlling for their relatively longer work hours.

About 26% of employees with irregular or on-call schedules report “often” experiencing work-family conflicts, compared with 19% of rotating or split shift workers and only 11% with regular schedules.

Irregular hours are also moderately associated with higher work stress, and more so for hourly workers than for salaried workers. Moreover, irregular shifts also diminish time for important parent-child interactions crucial to promoting children’s development.

Hopeful Signs

The announcements by retailers such as Gap and Abercrombie offer hopeful signs this harmful practice will soon be coming to an end.

Employees at those two retailers, for example, will soon be receiving notice of at least one week – and sometimes even up to two – of their work schedules. At Abercrombie, employees will be able to opt in to taking last-minute shifts, if they are interested, by responding to email alerts.

Such accommodations are sure to help many employees’ planning for household spending, daycare and classes. Many employers are starting to make changes on their own, perhaps prompted by the New York investigation or the looming prospect of passing national legislation that would create a legal right to request more advance notice or more predictable schedules.

The connections to work-family conflict, higher stress levels and potentially reduced productivity on the job themselves make for a strong “business case” for curbing and eventually eliminating the nefarious practice of on-call scheduling.

They also underscore the need for more scrutiny like the kind we saw from the New York attorney general and the adoption of preventative public policy measures such as the Schedules that Work Act. Many states and municipalities have adopted or are considering such reforms already, such as San Francisco and Minnesota. Let’s hope they prompt more employers to do the right thing, and adopt them on their own.